The current crop of Radeon cards aren't shabby, so your comment only applies to anything with integrated graphics. Besides, we now live in the world of eGPUs.
No one is going to be playing anything serious on the Magic Mouse, and it's not due to it's tactical response. The keyboards are fine, and that's what the Logitech G13 is for.
Funny, pretty much everything I play has always been launched on PC and Mac simultaneously. And for titles that aren't, that's what Bootcamp is for.
I have a life, a career, a girlfriend, two cats, and I don't crouch over my computer. I've designed my desk and chair to strike a good balance between ergonomics and economics. I can't speak to Civilization 6 as I don't play it.