As much as I love hacking with various things, there are reasons why I buy "closed products" for myself and for my family. I like to do hacking when I want it (with ESP32, rpi etc). I don't want to be forced to serve as a free IT support guy anytime someone presses a wrong button. When it comes to gaming consoles, I want them to serve reliably to my family. The game console must be fun, optimized for best experience…
Yes, SteamOS is just that. A system that is easy to rollback if you mess things up. And you have to go deep under the covers to mess things up (switch to desktop mode, disable readonly system partition, modify wrong files).
Valve should really focus on improving the polish of the steam store, as that abomination of a (react ?) frontend breaks often in very surprising ways.
SteamOS as a console system is close to a 9/10. As far as polish of steam app/store and the ux, a fair 7/10.