That was no "revisionalism". When GSC first came out they were wildey enojyed b the fans who played them and actual critics heralded them as just as good if not better than RBY. As the fans got a bit older, we began so see the flaws. There was definitely disagreement on how much the flaws (really only the level curve) actually mattered, but GSC were still considered enjoyable and respected as excellent games for the time they came out. The HGSS game out it it was universally considered on of the best Pokemon games ever.
The only thing that changed now is Merrick. Even Pokechallanges Video wasn't that bad since he actually did release some good points (including how lame the Rocket Plot Ending was which rarely came up before hand). However he exaggerated several things in his video and because most of his fans are zoomers who didn;t play GSC they look everything he said at face value. (they actually fell for the pic were he replaced every single Johto Pokmeon used by the Bosses with Kanto mons, proving that they know literally nothing about the game they love to shit on).
Then Merrick post his infamous posts about Johto and suddenly Johto because the worse game in history and the scapegoat for every thing wrong with SwSh. "Johto relies too much on Kanto when Galar has no culture outside of worshiping "LEONS UNDEFEATED CHARIZARD." "Johto is small even though Galar is literally a hallway" "Crystal killed Pokemania even though Dexit divided the fandom" "Dexit had to happen became of Stantler" "Team Rocket was pointless in Johto when Galar has to stupidest villain plot in the history of the franchise and Rose is possibly the stupidest person in the history of RPGs"
THIS was when Johto fans calling hating Merrick and developing victim complexes. Its basically mechanism for being attacked for now reason. It was all so sudden and out nowhere that one schizo assumed that TPC had to be paying people to behave this way