It's the chemistry that makes the content when it comes to group let's play type channels like AH and FH. The moment the chemistry and the fun takes a backseat to the business end of things is when the decline starts. People get replaced, the chemistry goes, everything starts to feel forced, but they get stuck in a loop of trying to recapture what once was.
Channels like these should rebrand and start anew once enough replacements happen that it's no longer the classic ensemble. You can keep calling it Achievement Hunter or Funhaus, but it's not.