The issue comes down to how the device interacts with your computer. Just like the original version, the new Steam Controller has no native Windows drivers. This means the hardware relies entirely on the Steam app to function properly. If you do not have the game running via Valve’s storefront app, your shiny new gamepad turns into a useless piece of plastic.
Gamers Nexus also reported this and there are a lot of other news outlets also covering this. It is kinda the same as with the steam deck where I noticed that the inputs just don’t work until steam is launched. I really don’t like that I have to have Steam running for this controller to work. I don’t know if it is a dealbreaker for me, yet, but it really put a damper on my enthusiasm about it
I don’t have the impression that supporting xinput/directinput is a time consuming effort. Yeah extra buttons and trackpad wouldn’t work, so what? The community will make something long term for Linux/Windows I have no doubt, but this was an easily avoided L on good will PR.
Personally doesn’t matter much to me, I have 8bitdo controllers already. After owning Steam Deck for years now I really want the trackpads and gyro wherever possible.