Steam Machine failed because nobody made them and what we did get was overpriced for the performance delivered. There was no reason to buy or make a Steam Machine over a standard PC, thus no audience for publishers or devs to care about. The Deck delivers something people want and people are buying it and using it.

That said, I think most of us, except for the die hard purists, are fine with Proton compatibility being the main target for companies. As long as a game runs as well as it does elsewhere without restrictions or inconvenience, most of us are happy and don't care about the technical details of how it's running.