...You're really missing the point ya know. Multiple series have had their moments of fame, big ones at that, before falling from that fame. Examples include Bleach and Toriko. Wanna know what happened to them during their decline? Toriko was cancelled, and Bleach either ended because of Kubo's poor health, or because it was cancelled. From what you've been saying, they could have replaced both mangaka, but they didn't. Shueisha would rather cancel a series before switching mangaka, which they can't because they obviously would have in these situations. Oh, that's not including the fact that multiple other mangaka ended their series by themselves when they were done, such as Matsui, the mangaka for Assassination Classroom, or Toriyama, the mangaka for Dragon Ball. And you have yet to provide an example of mangaka's getting booted and replaced yet, so can we really trust your word? Still though, this conversation ends here, as it'd probably be unwise to continue derailing the match.