I think the FGO haters have a bit more of an argument in the sense that the Persona games have legitimate merit to the point where "Persona" is a name that gets people excited just due to the fact the games are so beloved, whereas FGO is more of a thing that you "put up with" in order to extract the morsels of good from. I do know that there are people out there who legitimately have fun with most if not every aspect of FGO and I do not mean to devalue these people however.
That being said the FGO hateboner basically extends to all of the Fate side at this point and some people dislike aspects of FGO that I feel are unjustified just due to the fact that "it's FGO". If FGO was completely worthless then something like LB6 wouldn't exist - fan engagement on the level of GUT wouldn't exist.