Somebody recently posed this question on Quora (https://www.quora.com/What-happened-to-the-girl-who-played-Marcia-Brady-on-The-Brady-Bunch-Why-wasn-t-she-a-movie-star). I naturally assumed that Maureen's issues with substance abuse (https://pagesix.com/2018/09/19/inside-maureen-mccormicks-battle-with-drug-abuse/) played a major factor (https://www.quora.com/What-happened-to-the-girl-who-played-Marcia-Brady-on-The-Brady-Bunch-Why-wasn-t-she-a-movie-star/answer/Jon-Mixon-1) in her lack of stardom if you want to call it that beyond The Brady Bunch. Maureen also may have simply been a victim of typecasting (https://outsider.com/entertainment/the-brady-bunch-maureen-mccormick-revealed-blessing-curse-being-marcia-brady/) in that it was really difficult for people to see her (https://www.washingtonpost.com/archive/lifestyle/1992/06/08/the-brady-boomer/684b0726-a5f8-4576-b08a-916548a3e756/) as anybody besides Marcia Brady.

I always thought lack of height hurt both her and Eve Plumb. Maybe just to petique for bigtime stardom. Some sites exagerate her height at 5'3" and 5'2, but I bet she was only a tad over 5'.

For sure! She tells the story she blew several major motion picture roles because she was high on coke. She even showed up late for the Brady Bunch Variety Show.

As others have said (https://www.datalounge.com/thread/33158753-growing-up-brady-the-tv-movie-), Maureen seemed to be the embodiment of the sweet and athletic California girl next door. And in the last few seasons of The Brady Bunch, she was gorgeous during, when she had matured a bit and had the really long hair. She had a Peggy Lipton (https://www.google.com/search?sxsrf=AB5stBhVMDwVPMqULWni_dWKmiZyta592w:1688465453960&q=Peggy+Lipton+The+Mod+Squad&tbm=isch&sa=X&ved=2ahUKEwiJ5uT85_T_AhWemmoFHXzICh0Q0pQJegQIChAB) or young Cybill Shepard (https://i.ibb.co/TRpqYcW/18-EE3776-338-A-4-B8-D-97-E8-22-F10-EB44929.jpg) vibe during that time period. It's within reason to believe that Maureen could've made the leap to actual starlet, had the drugs not derailed her.

As others have said (https://www.datalounge.com/thread/33158753-growing-up-brady-the-tv-movie-), Maureen seemed to be the embodiment of the sweet and athletic California girl next door. And in the last few seasons of The Brady Bunch, she was gorgeous during, when she had matured a bit and had the really long hair. She had a Peggy Lipton (https://www.google.com/search?sxsrf=AB5stBhVMDwVPMqULWni_dWKmiZyta592w:1688465453960&q=Peggy+Lipton+The+Mod+Squad&tbm=isch&sa=X&ved=2ahUKEwiJ5uT85_T_AhWemmoFHXzICh0Q0pQJegQIChAB) or young Cybill Shepard (https://i.ibb.co/TRpqYcW/18-EE3776-338-A-4-B8-D-97-E8-22-F10-EB44929.jpg) vibe during that time period. It's within reason to believe that Maureen could've made the leap to actual starlet, had the drugs not derailed her.
I just read the book on the Brady Bunch Variety Hour. Many dabble in drugs but as early as 1977 it was impacting her work. She would show up late or not at all. The producers actually cut an opening scene without her because she was not there. When she did show up, the producers yelled at her in front of everyone. The entire cast just stood there in silent support. They were working so hard and she was impacting all their hard work by not showing up. These antics continued into the Brady Brides which was even harder to shoot because of her substance abuse. Its really sad but thankfully she turned it all around. She definitely could have been a major movie star.

For sure! She tells the story she blew several major motion picture roles because she was high on coke. She even showed up late for the Brady Bunch Variety Show.

Correct me if I'm wrong, but Maureen's drug abuse was pretty rampant by the time that The Brady Brides rolled around in 1981. I don't know for sure if that was one of the reasons why it had such a short run. But it was none the less, apparent that her drug use by that point, was out of control and held up production several times.

This sort of explains why her part in A Very Brady Christmas was an underwritten one given that Sherwood Schwartz and son Lloyd didn't know if she was 100% reliable.