I agree. I buy any game I can on GOG or physical media, but still use steam. The only reason I’m fine using steam is that I have backed up every game I own, and there are piracy tools that can break steam’s DRM. This way, if valve disappears, I can still play all my games without worry, except for the multiplayer parts of games that had multiplayer using steam servers exclusively.
However, there already exist emulators that let you play those multiplayer games on LAN without a connection to steam or the internet, so I’d imagine folks will figure out a hostable version for over-internet play if the need arises
Steam has DRM. But there are 3rd party programs that can bypass that DRM. So if you have the game downloaded, then you will be able to play your games forever, even if valve goes under and the internet breaks. You’ll technically be pirating the game at that point, but I personally have no qualms with that.