As I understood GP's comment, the crux is "a very wide range of users."

Right now Steam Deck works because of a focus on a very specific use and users. A general purpose desktop requires a lot more, and right now even the most mature linux desktop (GNOME, Plasma etc) have their rough edges and learning curve.

Steam deck is currently my primary computer. You just try to not use sudo at all. So I use nix to install all my software. From firefox to htop. It can get annoying because one of my scripts was trying to detect Mesa the other day and didn't work with nix installed mesa, otherwise it's perfect.