the reason things like zack and cody and waverly place worked is because they were simple concepts that you could do a lot with. two twins live in a hotel. the same twins live on a cruise ship. wizards and other fantasy creatures exist in an urban setting. Nowadays Disney and Nickelodean sitcoms are all like ‘this family has a dog that can eat metal’ and they expect five seasons out of that.
The sitcom genre isn’t the issue, it’s people expecting plots that would normally only work for one episode of a sitcom to work for an entire series.