Why is Project Sekai so hated by other Vocaloid fans?

Why do so many Vocaloid fans hate Project Sekai? It would be one thing if they just didn’t enjoy the game play or plot, but a lot of fans get pissed even at the mention of it. I know a lot of people complain about the fandom but from what I know a majority of the fandom is children and teens. All the Vocaloid fans I’ve ever met found out about Vocaloid as a kid so why do new fans who are kids get this hate? And I know Project Sekai players can be toxic but 1) it’s a video game with multi player of course it’s going to be toxic 2) the fandom is mostly comprised of children and if you’ve ever been in a high school or middle school you just know that those guys are petty assholes. If there is anything I just don’t know about the fandom that makes it so hated could someone explain.