I think it started very strong in season 1, then season 2 is where the cracks are starting to form. Charlie feels more and more like Zach's self insert, the short episode format means they can't tell actual stories in a decent amount of time (best seen with Rotten and the Halloween episode), the "haha realistic conversation" jokes are beginning to run thin, and, this is a big one, it's starting to become a YouTuber cameo party. I get letting your friends jump in and do some voice acting but when people are having polls and discussions about who should be next the guy for a one off you may have gone too far.