No one. I've tried arch and realized that's good if you are a geek investing time in your own system not caring if it's in a good known state and having plenty of time before any upgrade. I'm on NixOS willing to switch to Guix System (but not doing so, so far, simply because it does not support various stuff I use, starting from a quick good zfs encrypted root support, Rustdesk client and server etc), willing especially due to last community issues who have put the development on the verge of something potentially really bad, BUT both are declarative systems. I only have to write a config, they build themselves out of it. I can replicate, change and came back, always having nearly a fresh install.
No need to backup the system, only my data, config included, no need to keep a bug ridden giant homegrown install scrip to replicate (trying to) my system on hw changes or wasting time with Ansible and Salt YAML/python hell to do the same with no less bugs and real guarantee of successful replication.
I have an *nix background but a bit tired of GNU/Linux since MANY years, I've tried switching back to FreeBSD a bit of time ago, but it's modern hw support is not enough for my needs, orphaned of OpenSolaris/IllumOS (with zfs a bit integrated into the system, meaning installer/package manager able to produce boot environments and clones reliably and easily enough) I've found in NixOS a relief. The Nix langue for me is as digestible as Haskell, something close to digesting broken glass, but for my mere needs it's usable enough. I only dream the community find a relief of Guix start to care the desktop a bit more, since HPC is a nice thing but... To have a model spread we need the desktop, Microsoft know that very well...
Long story short: the point is not "avoiding regular painful fresh installs or dirty cross-release upgrades" but making upgrades NOT PAINFUL and easy to reverse without issues. All the time in all system an update can fail, that simply must be not a issue. A casual user have no reason to invest much time in his/her own production machines, investing to learn once, profit forever must be the model. Is something breaks the casual user just have to reboot and wait a bit of time if the breakage is caused by upstream changes of waiting for when he/she have time to see what's part of his/her own code needs to change. No issue meaning not much more than a simple reboot. No time wasted with zfs diff and so on to quickly fix your system because you need it tomorrow morning and you have updated late night on the go. Also there MUST BE NO REASONS to waste hw resources and running Babel's towers like docker and co just because some apps are damn complex.
In NixOS deploying a classic LAMP app is (if packaged) servicename.enable = true; in most cases. Few LoC otherwise, DB, NGINX, PHP, ... no matter what get set up issueless without downloading and running a Matryoshka of distros with lxc/d wrappers running binaries made by unknown people on internet, with often not updated dependencies, forgotten ssh authorized keys and so on.
NixOS and Guix are the classic IaC applied to the OS.