VRChat mods include things like general QOL improvements, but also most accessibility features are mods. Things like preventing flashing colors to avoid seizures.
They want to ban them because they compete with VRC+, their premium service.
At least one mute person was banned from their Discord for saying they need to be able to use muteTTS to talk to other players, which sends... quite the hostile message to players with disabilities. VRChat has practically no accessibility features beyond their fairly basic rank-based privacy settings (and of course there's a mod to enhance those considerably).
They want to ban them because they compete with VRC+, their premium service.