Omg that’s a valid concern. This is exactly what xero are doing right now. Finding every little place they can charge and adding fees for developers left, right and centre. A megalomaniac leader has led xero to complete enshitification, and, with the wrong leader, steam could end up on the same place.
Exclusives are cancer to gamers, and lock people into ecosystems. All games should be available on all appropriate platforms, for greater consumer choice.