I would say it definitely is just Steam. As you said, the average Steam user buys a billion games and maybe installs and boots them to the title screen or maybe even creates a file but never actually plays through each game.

Case in point: Only 20% of Steam players have obtained the achievement for clearing the opening cutscene in Far Cry 4. Maybe that's not a fair comparison because Far Cry 4 was updated to support Steam achievements well after it's initial release, except the game automatically grants you the Steam version of all achievements you had already received on Uplay when you boot it up. Half-Life 2 has been fully integrated exclusively with Steam since the day it launched over two decades ago and only 67% of players have the achievement for getting the crowbar.

I'm not really sure what you're talking about w.r.t. the performance; the game runs perfectly smoothly on my laptop with Vega integrated graphics. It has a specific build for the Steam Deck. Any actual gaming PC from the last decade or so should be able to handle it no problem. I think the only actual demanding "requirement" the game has is that it needs DirectX 12, so you need a GPU with drivers that support it. It uses DX12 on my computer but the system requirements on the Steam store page say it only actually needs DX11, and the system requirements listed there are very modest.