"Oh but nobody's talking about this other shitty thing so everything must be permitted" is...certainly a way to approach the world, but not one to which I subscribe. Nor should you.

And Steam doesn't, and in fact cannot, prevent you from installing GOG Galaxy or downloading games from itch.io. (And devices like the Steam Link will happily play games sourced from GOG Galaxy or itch.io through them!)

This is tiresome. I will not reply to you further.