Well, calling the jump from 2d to 3d an "upgrade" straight out is kind of...debatable, but of course i'm not gonna go ahead and say something as bullshitic and that, i get your point...and to that point, i've got to say... it's pretty difficult for devs who work with the Unity engine version that's not il2cpp based to optimize it..., so they end up being quite demanding.
I've been looking into this, by the way, there seems to be one mod for MelonLoader called RuntimeGraphicsSettings but aimed at il2cpp based games, which was made for this VRChat game thing, and as name implies, allows tweaking a little beyond to get those extra FPS. Things like textures, shadows, lighting, etc all that shite.
Anyway, sadly, i haven't found anything for games like this that are not il2cpp based.... hmmm...