According to what has been written (https://www.quora.com/Why-did-actor-and-singer-David-Cassidy-known-primarily-for-The-Partridge-Family-never-star-in-any-blockbuster-Hollywood-movies/answer/Jon-Mixon-1) on Quora:

Cassidy was an alcoholic - While his problems were manageable during the filming of the Partridge Family, as time went on, he became difficult to direct and undependable. Although he went to rehab several times over the course of his life, he was never able to overcome his problem.
Cassidy’s acting skills were, charitably, limited - Keith Partridge was basically Cassidy acting like himself. When he starred in Man Undercover it was simply him acting like Partridge again and the role REALLY needed more than that. Although Cassidy did a few pilots over the years following that, none were picked up for airing.
He really had difficulty with comedy - Although he seemed to be funny on The Partridge Family, when he was on other things years later, he really couldn’t stick the landing. This was particularly troubling as Cassidy’s career could have been far more successful had he been able to become a funnier performer.
He could never expand upon his time in Las Vegas - Cassidy spent years toiling in Las Vegas and unfortunately he never seems to have been able to have translated that into successful career in his later life. Whether or that was bad management or bad luck is not exactly clear.
Cassidy seems to have never recovered from the White City Stadium stampede - 800 people were injured in the 1977 incident and one teenager was killed. This seems to have haunted him for the remainder of his life as he was clearly troubled when he was asked about it decades later.

David Cassidy's acting in the Man Undercover series was decent enough, the pilot movie Police Story/A Chance To Live was fairly well received and if I remember correctly David got an Emmy nomination for his performance.

One problem with the Man Undercover series was the writing, scripts for most episodes were weak which is a reason why the series ran for only 10 episodes. The first three episodes are pretty good but the writing falls off after that.

Another problem with Man Undercover is that David was so typecast as Keith Partridge and when he tried moving on from that image to do a dramatic TV series, many of his fans tuned out because they would only accept him as Keith Partridge and not as an undercover police officer going after the criminals.

David's role in The Partridge Family was both a blessing and a curse, it brought him fame but after the series was over he had difficulty shedding that teen idol/pop star image.

I heard that Cassidy was considered successful with his time in Nevada. Something about reinventing himself three times.

He was so good in the Keith role though. No one else has come close in terms of comedy and dramatic acting, and singing talent for a similar role as this one.

David Cassidy Man Undercover https://www.youtube.com/watch?v=MIFrW3DJn_U&list=PL6VS9hLxLf3CgduLM_5BEbOixX07M-NxK

Less than average talent and a HUGE drug problem.

Its also rare for teen idols to break out.

He was so good in the Keith role though. No one else has come close in terms of comedy and dramatic acting, and singing talent for a similar role as this one.

He did do well in PF, esp. in seasons 2 thru 4. The show figured out how to make the comedy work with the three kids (the youngest two were "just there").

Danny was also a big part of the comedy success.

Less than average talent and a HUGE drug problem.

Its also rare for teen idols to break out.

It's also been argued (https://www.reddit.com/r/ToddintheShadow/comments/18ekgb2/which_artists_have_a_career_move_that_is_viewed/) that David's decision to go shirtless on the cover of Rolling Stone (https://www.rollingstone.com/culture/culture-news/why-david-cassidy-bared-all-for-annie-leibovitzs-cover-photo-shoot-128968/) magazine in 1972 wasn't a good career move since it destroyed his teen idol reputation and basically made him out to be a laughing stock in the rock world.

People who have addiction issues are a huge liability. They can slow down production, behave poorly and irritate everyone on the set.

Once you have a bad reputation, few people are willing to stick their necks out for those who are troubled.

People who have addiction issues are a huge liability. They can slow down production, behave poorly and irritate everyone on the set.

Once you have a bad reputation, few people are willing to stick their necks out for those who are troubled.

Ironically, Susan Dey by her own admission (https://www.deseret.com/1993/10/22/19072238/dey-admits-alcoholism-after-tabloid-exposes/#:~:text=Dey%2C%20who%20got%20her%20start,a%20big%20story%20about%20it.), was also an alcoholic (https://www.washingtonpost.com/archive/lifestyle/1989/10/05/susan-dey-light-years-from-the-child-star/bd4a2fa1-caaf-4a13-895d-ab99a831e0a4/) and she arguably, among the kids in the cast, had the best post-Partridge Family acting career, at least if you take LA Law (https://www.google.com/search?q=la+law+susan+dey&sca_esv=2f800a701f0b426f&sca_upv=1&sxsrf=ACQVn089_b9PeZE8T8TmJpFt4i1UdM1xNg%3A1712634623837&ei=_7oUZozcMvmawbkPxoaP6AU&ved=0ahUKEwjM14iTnbSFAxV5TTABHUbDA10Q4dUDCBE&uact=5&oq=la+law+susan+dey&gs_lp=Egxnd3Mtd2l6LXNlcnAiEGxhIGxhdyBzdXNhbiBkZXkyBRAuGIAEMgYQABgWGB4yCBAAGIAEGKIEMggQABiABBiiBDIUEC4YgAQYlwUY3AQY3gQY3wTYAQNIhhVQAFigE3ABeAGQAQCYAecBoAGiF6oBBTAuOC43uAEDyAEA-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-oAg&sclient=gws-wiz-serp#ip=1) into account.

Less than average talent and a HUGE drug problem.

Its also rare for teen idols to break out.

I recently membered that David was on (https://www.youtube.com/watch?v=AVFChowfji4) the original TV adaptation of The Flash (https://www.davidcassidy.com/fansite/TvFilmPages/TheFlash.html) that aired on CBS back in 1990 (with John Wesley Shipp as Barry Allen). David (https://dc.fandom.com/wiki/David_Cassidy) (sporting a really sweet mullet by the way) played (https://arrow.fandom.com/wiki/Sam_Scudder_(Earth-90)) the villain known as Mirror Master (https://en.wikipedia.org/wiki/Mirror_Master).

I've listened to a lot of David's music and found him to have a very good voice and he performed well. I think he's underrated and discounted as a singer.

I don't know for certain that music was more important to him than acting, but from what I've read he was concerned that his friends were not taking him seriously as a music artist due to the Partridge role.

I doubt that the Rolling Stone cover harmed his career in any substantive way. Women who thought he was attractive continued to view him that way, and as far as his music career, harsh critics had already discounted his talent -- nothing changed in that regard.

David Cassidy Man Undercover https://www.youtube.com/watch?v=MIFrW3DJn_U&list=PL6VS9hLxLf3CgduLM_5BEbOixX07M-NxK

I never watched (https://books.google.com/books?id=EQEiQKfY6G4C&pg=PR10&lpg=PR10&dq=David+Cassidy:+Man+Undercover&source=bl&ots=kUZzhjblmq&sig=ACfU3U2NsT8cn4jcHQaqF99FP50LpDCc9A&hl=en&sa=X&ved=2ahUKEwj0--K51eyHAxUk5MkDHYEOGwc4RhDoAXoECCYQAw) David Cassidy: Man Undercover (https://forums.stevehoffman.tv/threads/partridge-family-appreciation-thread.971004/page-8#post-31312901), but from what I gathered (https://web.archive.org/web/20061031125223/http://www.jumptheshark.com/d/davidcassidymanundercover.htm), it was (https://en.wikipedia.org/wiki/David_Cassidy:_Man_Undercover) you could say, like a proto (https://www.google.com/search?q=David+Cassidy%3A+Man+Undercover+21+Jump+Street&sca_esv=36263895b7e20958&sca_upv=1&biw=1600&bih=773&sxsrf=ADLYWIIg7KzFDw5CJ0lftmW2ZBnEP7fHEw%3A1723370029992&ei=LYq4ZqiiPMW8p84Pg5-KmQ0&ved=0ahUKEwjo7NDT1eyHAxVF3skDHYOPItMQ4dUDCBA&uact=5&oq=David+Cassidy%3A+Man+Undercover+21+Jump+Street&gs_lp=Egxnd3Mtd2l6LXNlcnAiLERhdmlkIENhc3NpZHk6IE1hbiBVbmRlcmNvdmVyIDIxIEp1bXAgU3RyZWV0MgUQIRigATIFECEYqwIyBRAhGKsCSPoZUMMDWNwYcAF4AZABApgB5gSgAbkeqgELMC42LjEuMy4xLjK4AQPIAQD4AQGYAgygAtIYwgIHECMYsAMYJ8ICChAAGLADGNYEGEfCAgQQIxgnwgIKEAAYgAQYFBiHAsICBRAAGIAEwgIGEAAYFhgewgILEAAYgAQYhgMYigWYAwCIBgGQBgmSBwsxLjUuMi4yLjEuMaAHyDc&sclient=gws-wiz-serp)-21 Jump Street.

He was so good in the Keith role though. No one else has come close in terms of comedy and dramatic acting, and singing talent for a similar role as this one.

Somebody wrote (https://www.dvdtalk.com/reviews/35059/partridge-family-the-complete-third-season-the/) that David Cassidy actually had what it took to make a terrific light comedic lead. Unfortunately, he was pigeonholed as a teen idol and the studio system was no longer intact to take care of him and shepherd him through a film career.

Why did actor and singer David Cassidy, known primarily for "The Partridge Family", never star in any blockbuster Hollywood movies? (https://www.quora.com/Why-did-actor-and-singer-David-Cassidy-known-primarily-for-The-Partridge-Family-never-star-in-any-blockbuster-Hollywood-movies/answer/David-Holliday-27)

Had several strikes against him.


Although he was a heartthrob in the early '70s as the decade progressed, his slight of build, sweet smiled, sensitive guy was no longer the rage-by 1977, the draws were Clint Eastwood, Sylvester Stallone and Burt Reynolds-macho men. Also extremely popular were serious and extremely talented actors-Al Pacino, Robert DeNiro and Robert Redford. The exceptions were proven mega talents like Mel Brooks or Woody Allen.

His music was passé by the middle of the decade, while he still had fans, any potential movies would have been looked at critically by producers who remembered the last Elvis films. It is true that some singers had successful serious careers in film, Barbra Streisand, Kris Kristofferson and to a much lesser extent Kenny Rogers, Glen Campbell and Johnny Cash. But their music was still popular and topping the charts and they were more serious.

Personal demons, he had serious drug and alcohol problems and was deeply traumatized by a tragedy that occurred in May 1974, where 800 fans stormed the stage at his concert and a 14 year old girl was killed. That kind of obsession among fans would have broken anyone.

That said, he did have some talent, but it wasn’t blockbuster movie talent. Let’s face it, some people are meant to be film stars, others Television stars. Just ask the cast of Friends.

He had some good roles on television. His guest shot on the popular series Police Story, earned him an Emmy nomination. Honestly he might have had it had he not been up against the sentimental favorite and immensely talented Bernard Hughes who of course won.