Steam as a platform is completely, utterly atrocious in all regards. Their client is ancient, outdated, and barely usable, there's no content quality filtering,

Steam as a platform is completely, utterly atrocious in all regards. Their client is ancient, outdated, and barely usable, there's no content quality filtering, the greenlight program is a failure that only succeeds in bringing complete bottom of the barrel dreg in 99% of cases, even from a developer's point of view the platform is just a major PITA. But it has the first mover advantage and that is really everything. Even platforms that are infinitely better, have better tools, support, and pricing (such as itch.io that doesn't require a cent to publish your games) are heavily disadvantaged just because it takes extra work for developers and gamers to adopt them. There's no easy way out of this and Valve can continue being lazy and make major slip-ups every year and there's very little others can do to endanger their heavily entrenched position on the gaming market. As far as PC (or GNU/Linux in particular) gaming is considered, Steam is everything, and it's not going to change any time soon.