aesthetics, build quality, assurance that it’d all work smoothly, the whole experience just wouldn’t be the same

You’re right, it’d probably be way better…and it would be customized to your preferences and price point.

which is to say nothing about the fact that SteamOS doesn’t really work on hardware that’s dissimilar to the steamdeck…

You’re right again, you could use Bazzite or Nobara or Chimera and have an even better experience. Ask me how I know.