It works great! And I can use the deck as a normal PC for web browsing/slack/discord etc.
There’s nothing I need windows for anymore thankfully.
Getting your hardware working right is still the biggest problem. The games work great, occasionally audio/video driver issues necessitate some fiddling. (advantage to the Deck is that this goes away.)
The Windows API is just that: an API. An interface. Who cares whether it's implemented by Windows or Linux or whatever else?
It was an explosive hit of DOS-based PC gaming market nevertheless.
Even if it didn't, the number of people for whom HDR support is a make or break feature is likely not very high. Non developers use linux daily with the steam deck. I set up my mom with my xps 15 with Ubuntu on it when her laptop mobo died. While she wasn't a huge fan of having to learn a new UI, she was able to use it without issue for facebook/email/netflix/taxes/online banking for a few months until a good deal on a replacement came up and I got my laptop back.
I don't think if you are objective you can call linux so far behind windows. They are on par, each has their own annoyances and strengths, but for the average person they are just web browsing machines anyway.
The Steam client works just fine, although I do have to "force compatibility" and choose Proton. So far the games have played fine, including big games like Cyberpunk 2077.
For non-Steam, I'm using the Heroic Game Launcher, and it works great. I'm not missing any games, and I certainly don't miss the Windows BS.