I have clarified that I meant controller support in the Steam games themselves. Some of them work well, some of them not so well. Others need to be configured. Others only work with a Steam controller. I wish everything worked well with DualSense, especially since I really like its haptics, but it's basically on the many (many) game developers to provide the same kind of controller support that is standard on consoles.
Are you sure you have steam configured right? Because with steam input you can get proper xbox controller emulation on games that don't support PS4/5 and NS controllers. It's not perfect but you should never be stuck if you don't have an xbox or steam controller when running games inside Steam.
Lots of games on Steam simply don't have great (or really any) controller support. Steam controller can sort of play some of them though since it can emulate mouse + keyboard etc.
My experience with Steam Input is ... OK in some cases. It's annoying that it seems to break games that actually do support the DualSense properly (though full haptics only work in wired mode) like FFXIV.
Thanks for the clarification. I've into that a couple of times - Steam's button remapping helps sometimes, but you'd have to remember which controller button the on-screen symbol maps to.