Specifically, the types that were aired on Cartoon Network, Disney Channel, and Nickelodeon? It was in this era (https://www.youtube.com/watch?v=kAGGsO23z_k&lc=UgyCKMS2HJNX3vsTVmR4AaABAg) that saw more or lesss, Disney Channel following (https://tvtropes.org/pmwiki/pmwiki.php/AudienceAlienatingEra/TelevisionNetworks) the High School Musical and Hannah Montana formulas with teenyboppers as their target audience, the real beginning of Nickelodeon's slow decline (https://tvtropes.org/pmwiki/pmwiki.php/NetworkDecay/MajorShiftsThatFit), and Cartoon Network releasing half-baked live-action shows and straying too far (https://tvtropes.org/pmwiki/pmwiki.php/NetworkDecay/TemporaryShifts) from their roots.

When it comes down to it when you ask any person what part of the 2000's was the worst for TV people will most answer 2006-2010 because that was truly the dark age for kids TV. Because when you get the general picture TV shows that were aimed at younger kids were few and far between and now they were attracting the new audience which was older kids in the 11-13 age group and teens in the 13-17 age group. And when the TV stations noticed this they started to appeal to the older kids and teens by having programming and content that suited them. Nickelodeon was actually the first cable channel in history to do this when they launched The-N which is now TeenNick and when it came out The-N recieved rave reviews and it was a winner for Nickelodeon. And so after seeing how successful The-N worked for Nickelodeon Disney Channel decided to follow suit by attracting the new teenage market. And part of it and a lot of why they did this is due to the premiere of High School Musical and when High School Musical made it's debut on Disney Channel it set world records and another thing that attracted teens to High School Musical was you had actors who were crush-worthy for teenage girls. I still remember when High School Musical came out and almost every teen magazine from Tiger Beat to Bop had posters of Zac Efron and Corbin Bleu and I remember having a crush on Corbin Bleu when I heard about High School Musical and based on that success they managed to make three High School Musical movies and the third movie was in theaters and it also spun off Sharpay's Fabulous Adventure which was a smash movie as well. Once they saw that High School Musical was a hit Disney Channel did the same thing with Hannah Montana and Miley Cyrus became a superstar for Disney and they knew that this was the way to attract the teen and older kid audience. Disney Channel worked it's magic again with another movie which was Camp Rock and like High School Musical it was a smash hit and made a star out of Demi Lovato and it too like High School Musical released a sequel as well but the sequel wasn't as successful as the High School Musical sequels. And so with shows like That's So Raven The Suite Life Of Zack And Cody Sonny With A Chance that proved this was the new image of Disney Channel. Nickelodeon had always wanted to attract the teen audience ever since the 90's and so when the SNICK lineup debuted Nickelodeon had that chance with sitcoms like Kenan And Kel My Brother And Me and Clarissa Explains It All Salute Your Shorts Roundhouse and Hey Dude little did we know that Nickelodeon would adopt a new image drawing themselves away from the cartoons/game show lineup later on. When Nickelodeon debuted ICarly they knew that this was the new audience that attracted TV now and they previously had a sitcom named Taina which was about a singing star and they recycled the same show but named it Victorious and it made Victoria Justice one of Nickelodeon's biggest teen stars. While Spongebob Squarepants is still the king of Nickelodeon cartoons even though Nickelodeon has no interest in cartoons anymore. And finally Cartoon Network tries very hard to attract older kids and teens but what I think their audience they are attracting is college age people and the only cartoons the older kids watch on Cartoon Network are Teen Titans Go and when Adventure Time debuted it was a strong hit with kids and teens but once Adventure Time ended Adult Swim gained most of the teen audience for Cartoon Network. But as TV continues to impress the world I think most of the older kids and teen programming will move to streaming now
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Probably Nickelodeon's biggest problem in the (https://youtu.be/8sr1xwwmcoo) 2000s-early 2010s (in other words, the time period in which Cyma Zarghami was the channel's president) in a nutshell is that they were either trying too hard and spending too much time cashing in on trends, whether it be popular internet stars like Fred or rival networks like Disney Channel, or them simply not understanding their target demographic.