Epic already does that and has a number of exclusives to their store, like Alan Wake 2. They also will pay devs to have it exclusive to their store for a year.

Yeah, that's why the monopoly argument is important. Not because monopolies are illegal, but some new competitor being aggressive is different from the established robber baron squashing potential competition using its establishment.

Epic as a game store is very much not a monopoly by any means. Game consoles are certainly an argument, but thus far none are dominant over the other. It would mostly be a problem if a new console jumped in and Sony/Microsoft teamed up to hardball it out.