Steam isn't blocking anyone from competing as far as I'm aware. It's just that most customers don't to switch to a new platform because none of the competition is better than they are and we don't want to have to juggle multiple launchers. If Steam started being assholes to the customers or developers stopped putting games on there we'd look at other options.

Supposing Steam is a monopoly what remedy do propose that wouldn't make the user experience worse for their customers?

Be pedantic as you want, steam makes no bones about it being 30%.

And unlike other marketplaces, Steam doesn't demand exclusivity. If anything they encourage publishers and developers to put their content on other storefronts or other alternatives that are available. Unlike, say Origin, Epic Games or what ever the hell Ubisoft was trying to.

Steam taking 30% may seem steep but they do a lot of support for developers in addition to the largest PC marketplace out there, complete with built in communities around new games where developers can directly interact with players of their game(s.) As long as the game works as advertised, Steam has historically done very little to penalize or inhibit developers on the market place. And nearly every case of it that has come to light has been admitted to be a mistake and rectify, such in the case of Hatred, or has been transparent about a third party stopping short of legal action, such as in the case of the Mastercard censorship scandal.

Compare that to Epic Games, who provides basically no support to developers, no community features or anyway to connect with other people who enjoy that specific game or those like it, and actively spies on users and is somewhat infamous for downloads servers to sporadically go down or corrupt a game require multiple attempts to ensure the product works. All while taking 12%

Steam isn't perfect, they've screwed stuff up and missed a few bad actors in their midst before, but overall they are very pro-consumer and provide an open and fair platform where indie games can get showcased on the front page of the store as much if not more so than AAA games with million dollar advertising campaigns. Many of those indie games never would have seen the light of day without steam.

Steam is basically today what Netflix was in the late 00s/early 10s. A massive collection of content for people to enjoy that actively opposed the idea of exclusivity or preventing other. Where Epic is actively trying to push gaming to where Streaming is today by trying to bribe publishers and developers with better deals and kick backs if they agree to put their game on EGS exclusively for 6 to 18 months if not permanently.