Would you say that a basic game, like a canvas game should use mutable state?
2d physics. Standard side-scroll
Pretty solidly going to say not to worry about it. Games were made forever with a global mutable area for gamestate.
This talk has some good pointers on game dev. It's part of a much larger topic but the speaker is good. And there are gradients to avoiding mutation. Don't avoid it like the plague, just keep it in mind.