Valve's greatest contribution IMO is SteamOS.
If you have AMD hardware, it's (almost) foolish to not use Bazzite/Linux. (A distro that is identical to SteamOS, but is more friendly to desktops)
It's an infinitely better experience than Windows.
The one thing Valve really needs to do is work more closely with nvidia to get their Linux GPU drivers up-to-snuff. Right now, they're useable, but they are about a tier in performance lower on Linux and outright awful in DX12 titles, which is a reason I would prefer all developers abandon DX and just use Vulkan.
On AMD DXVK works AMAZINGLY well, but getting rid of a translation layer would be a benefit to everyone.