The only benefit for a normal desktop user, who never plans to write code (or deploy stuff on multiple PCs) is that immutability makes updates far safer and easier.
However this is the single largest weakness the Linux desktop has. Everyone can use a linux computer, maintenance though is always a problem. No one has succeeded at making a regular distribution that never needs command line intervention and a degree of knowhow to unbreak. (not counting Chrome OS) Maybe someday soon we'll have an immutable distribution that's truly just install and forget. (with good DE options like the new cosmic or even a carefully put together Hyprland rice)