But it's more the configuration that I want to be able to adjust, or to recompile things. As a typical example, on alpine I always need to recompile sudo as their standard version doesn't allow PAM which I need. On an immutable system such tools would usually be in the immutable part.
I had problems with macOS when they switched to immutable (and if you turn off the protection it turns off a whole load of other things too). If I as much as changed the /etc/ssh/sshd_config it would revert with updates.
And really the traditional package system works totally fine for me.