You could separate the storefront from the distribution platform / client. Valve's ~30% cut is often justified by the visibility being on the Store gives you but you can't opt out of that while still reaching the captured audience that definitely don't want yet another client software bloating up their system.
No, you cannot. AT&T/Bell Labs was a monopoly - they physically controlled distribution networks that made it so you had to use them.
Valve does not. There is nothing that prevents you from simply selling your game without Steam.
And even if there wasn't, claims that Valve is a monopoly are factually false - there are many other storefronts that exist, and many games are published on more than one storefront at once. And, Steam does not gate an OS or platform like Microsoft and iOS do.
> But I’m being already aggressively downvoted with no counter arguments
Every one of your arguments is being countered (such as the claim that "relevance is anticompetitive" which isn't even false, it's nonsensical). Including this one.
> Defending a deca-billionaire is hard work, after all.
...and there's the emotional manipulation. It's pretty clear you're just a propagandist who has a grudge against Steam (maybe you work for Epic?), given that you're going up and down the thread with emotional non-arguments that try to redefine words, pull at peoples' emotions (like the billionaire comment), or just flat-out lie.
Except they do. They control the Steam distribution network. It may not be physical but you still have to use it to reach a large portion of PC Gamers due to network effects and no one wanting to run multiple clients.
Currently you have to also make use of their other services like the Store, and pay for them with a large sales cut, in order to use the distribution network, no matter if you want those services or not.
1. Being a monopoly
2. Abusing monopoly status.
Steam does control the vast share of desktop gaming. But has no influence on console (Xbox, playstation, switch) or mobile (android, ios). They are a monopoly.
But they don’t abuse their monopoly so they haven’t broken any laws.