So long as Valve remains private, the experience getting shittier in the name of more profits is a pressure that faces Valve but not necessarily an inevitably.

If Valve breaks the trust they have built in ways that Google and Microsoft have and continue to do, of course I will stop using them where feasible. Assurances mean nothing, I will respond to action with action of my own. Support more games for Linux, I will buy more of their games. Support bad practices like kernel-level anticheat, launchers in launchers in launchers, PSN, I will buy fewer of those games. I have an account with GOG (I have spent a little bit of money, I would more it Galaxy was available for Linux), Epic (I have spent $0 there because of Tim Sweeney's aversion to Linux) and Itch.io (has a Linux client). I can move platforms if Steam has a sudden change of heart tomorrow and becomes hellbent on screwing customers over.

I think that there is regulation to be had re: the ownership of games or minimum availability of service for what is paid on both the seller and consumer side. But "I'm paying too much for games because of Valve's monopoly" wasn't really on my radar of things that Valve is doing wrong.