I run Debian stable, and it's not immutable, but it is very unchanging. I don't worry much about system libraries and tooling.
The downside to that is that then userland application are out of date - in enters Flatpak. I run most GUI applications in flatpak. This has a lot of benefits. They're containerized, so they maintain their own libraries. They can be bleeding edge but I don't have to worry about it affecting system packages. I also get much simpler control - no fiddling with apparmor, the built-in Flatpak permission system is powerful enough.
The blind spot then is CLI apps and tooling. Usually it doesn't matter too much being bound to system packages, but if it really does, I can always containerize those too. I only do it for my PHP dev environment.