You keep making good points. Unreal Engine has been around since 1998. They've had a long time developing the engine and it makes it hard for other engines to compete. There are a few, but not many. They've invested a lot of money into making their engine the premium option and making sure consumers avoid alternatives that aren't as feature rich.
You can't put out a shit product and then cry about why people aren't buying it. It doesn't work for any market. Can try to coerce people with monopolistic practices of trying to deny product availability, but that'll only get you so far.
You clearly can coerce people with monopolistic practices. You're defending Valve over Epic, which Epic has a much smaller market share. You can call it anti-consumer if you want, but monopolistic? Yeah right. When one store is the default, devs have to sacrafice to not be a part of it. Again, I agree it sucks, but it's a monopoly by Valve, not Epic.
If anything if your argument is that it is hard then that just seems to bring to question of maybe a low cut actually isn't realistic if a company wants to make a feature rich launcher and platform if even a billion dollar company is finding it hard to accomplish.
There are two consumers here. There's consumers who purchase games, and consumers who utilize the product to sell their games. Epic gives a smaller cut to entice devs, because otherwise they have no reason to participate because all the game purchases happen through Steam.
It all sucks for the consumer, which is why monopolies are bad. We shouldn't be defending some company who's making tons of profit just because we are simping for their product. Steam is undoubtedly superior, but that doesn't mean they aren't monopolistic.