Over time I evolved to Debian testing for the base system and nix for getting precise versions of tools, which worked fairly well. But, I just converted my last Debian box to nixos
Servers and headless boxes use stable and all machines are updated regularly. Most importantly, stable to stable (i.e. 12 to 13) upgrades takes around 5 minutes incl. final reboot.
I reinstalled Debian once. I had to migrate my system to 64 bit, and there was no clear way to move from 32 to 64 bit at that time. Well, once in 20 years is not bad, if you ask me.
1) nix means I have to install a lot fewer packages globally, which prevents accidentally using the wrong version of a package in a project.
2) I like having a version controlled record of what my systems look like (and I actually like the nix language)
While I understand the gravitas of NixOS, that modus operandi just is not for me. I'm happy and fine with my traditional way.
However, as I said, I understand and respect who use NixOS. I just don't share the same perspective and ideas. Hope it never breaks on you.