The existence of one premier dominant platform is called a fucking monopoly.

Read the first sentence of the Cornell Law Legal Dictionary:

A monopoly is when a single company or entity creates an unreasonable restraint of competition in a market.

Restraint of Competition links to the FTC doc that defines what that is in a page titled "Monopolization defined" and it offers a two pronged test which is exactly what I've been saying all this time, they have to be the leader in their market which they have to have "gained or maintained through improper conduct."

Your lay interpretation informed by feelings that it's bad we have a market leader (and even there I'm giving you a huge gimmie because Google Play, GOG, EGS, Xbox, UPlay, and Amazon Games all exist and sell PC games in a digital storefront entirely absent Steam, and for stores that aren't absent Steam, as I noted before even games sold for use on Steam may not net Valve any revenue thanks to the ability of devs to sell their keys directly) is just not the correct interpretation for whether Steam is a monopoly. EA alone made almost as much revenue in 2023 as Valve did, which isn't an apples to apples comparison since EA does business a lot of places, but they're just one of a lot of big fish who don't always put money in Valve's pockets in the Digital PC Games Distribution market. Many devs sell their games as Steam keys on Amazon, GameStop, Newegg, Best Buy, Walmart, Target, and all the others I linked before and Valve gets nothing (Excepting maybe a freeloading user) from those sales.

Out of curiosity I went to check out my account to see what I had bought "from Valve" vs "not from Valve" on Steam and it turns out that I own 1724 games on Steam. We can break that down in the transaction history, but I'm not going to go line by line to figure out which are DLC and which are games so this next part won't add up to 1724, but I'm providing the number to give some context for the remaining numbers so it doesn't just look like most of my transactions are MTX or something silly where Steam is actually getting something. I think it is illuminating to show that I have only made 718 purchases through Steam, I have been gifted 70 games, and I have 209 transactions which were indicated to be "Complimentary" where most seem to be DLC but there are a few games in that mix, so let's be charitable and give Valve the whole lot those as sales even though they were likely nothing of the sort. I have in my transaction history 1152 transactions that are listed as "Retail" which is Steam's way of showing that I didn't get the game or DLC from them. In 16 years of using Steam, Valve has charitably gotten a cut of 997 interactions, while I have given Steam 0% of a transaction 1152 times. That means that Valve has gotten a cut for only 47% of the content that they provide me at the absolutely most charitable interpretation of the data. So far as my account is concerned, if they're monopolizing the market, they're doing a terrible job of it by letting everyone else out there take the majority of the money while bearing none of the costs for Steam's infrastructure and development.

You can dismiss the fact that there is a historical record of Steam often not being the cheapest place to buy a game, or you can claim that just because there is a dominant player we defacto have a monopoly, or any of the other insane claims you've made but the fact is that there isn't a finding of law anywhere stating that Steam is a monopoly and it's unlikely there ever will be because they just don't meet the standard defined even if you cut down the market to the slimmest possible framing.

Unfortunately, we have clearly reached an impasse where you refuse to acknowledge statements of fact as written and will just "blah blah blah" away inconvenient facts, so I suppose this is where we part ways. Hopefully the next time we meet will bear better fruit.