From personal experience, most big name authors I have come across tend to usually also be the ones who struggle the most with keeping the characters in character and heavily depend on using outdated cliches (one of the most well known Destiel fanfictions is an OOC mess that people have actually asked the author to publish and have printed out themselves). I tend to usually avoid their recs for that reason.

Maybe because at some point they get so big they no longer care about growing their writing since they will get praise either way Or they were always bad and people just ignore it for the sake of the familiar tropes.