the fact that valve is in such a dominant position that them refusing to sell a game can mean not only the game’s failure, but the shutdown of the studio making it,
There are games exclusive to Epic that do just fine. There are games on itch and GoG that are doing just fine.
If Steam not hosting your game causes your studio to shut down, it's not because Steam is being some unreasonable gatekeeper. It's because you're making something that there isn't any market for, or so little of a market that your only hope is to get it visible to as many people as possible so the tiny fraction of them that are interested can keep you afloat.