PC Gaming

What systemic issue? If you as a player don't like steam, you can just not use it. It's not like apple where the hardware is locked to a single storefront. Even the steam deck is open for people to get games from anywhere.

Developers are allowed to do whatever they like too, including not putting their games on steam as a form of protest. No one will stop you. They can even sell their games on multiple platforms and reduce the price where the storefront cut is smaller. The only thing they are not allowed to do is sell steam keys on their own store below the price on steam, which is completely understandable. The fact that they are allowed to sell keys directly (AFAIK for no cost) is already a huge boon.

The one's actually behaving in anticompetetive behaviour is Epic with paying devs for exclusivity to their store. This is forcing you to use the platform to play certain games without having any other options. Of course the devs taking the deal are also complicit but that is somewhat more understandable, being a gamedev is difficult these days.

The difference is obvious, ~~you don't have to be a genius to see it~~. Epic is the plague of modern capitalism and greed, where the product is kept afloat by an unsustainable inflow of investor money. The service is ready to enshittify the second the amount of users crosses a certain threshold. Then they will continue to fight with dirty tactics to keep users locked in for as long as they can. How long do you think giving away free games weekly to anyone can last. (Aswer: as long as the fortnite money is coming in)

Steam is an old type of corporation (for now anyway). They focus on making a good product for a "fair" price. Fair as in this is what makes the platform sustainable. If they were to charge exorbitant prices, there would be a huge developer exodus. But there isn't. Most devs seem to have come to a conclusion that paying this optional fee is worth it for that value that steam provides. This money allows them to reinvest in the platform to make upgrades, and yes, make profit too. What other reason would they go through all this trouble for?
Steam is also a privately held company, meaning they are not beholden to the short term vision of investors' pump and dump schemes. But to reiterate, literally no one is forcing you to use steam.

These days you have to capture a large user base with unsustainable prices/practices and then extract every cent for infinite growth. This is not just bad for users in the long term but also means setting up a "normal" company offering a good product at a "fair" price is impossible because everyone is buying the cheap unsustainable products essentially below cost.

I miss the times when a company would make a good product at a fair price and that would be enough.

Edit: that was unnecessarily harsh. I can see you want positive change but unless someone opens a FOSS storefront and pays for the work/distribution, steam is the best we have for now (as gamers). And reducing costs by ~10-20% is not going to make it better for us long term.