The point is not much the project per se but the concept, Infrastructure as Code, OS as code. So far NixOS is a relatively small ecosystem, in a complex community situation with the main sponsors, a mil-tech company, who have got a wave of backslash for debatable reasons, Guix System on other side it's mostly a French INRIA project focused more on HPC than anything else, so both have their corners, but they show a modern way to develop and deploy OSes as OpenSolaris (since it was before IllumOS fork) show the first integration of storage (zfs) and package system (IPS) and bootloader (with the boot environment concept), somewhat badly copied later by FreeBSD and partially on GNU/Linux with a set of scripts.

ALL OTHER OSes/distro are still stuck in the '80s in that sense and most people seems even unable to understand. On storage alone the famous "rampant layer violation" and the absurdity of btrfs and stratis "against" zfs are really good examples of blind tech reactionary behaviors by high skilled people and their outcomes a showcase of why we damn need to innovate instead of shooting ourselves in the feet switching from something obsolete to something even worse (like the now-almost-finished full stack virtualization on x86 and thereafter the paravirtualization/container mania still current) layering crap on crap with more and more unmanageable infra with enormous attack surfaces.

Another small and relatively known example: Home Assistant project: apart of their design, they choose to distribute a python application as a GNU/Linux entire distro because to the such move seems to be commercially sound and many others choose to follow them instead of simply pip-install HA in a local venv, wasting an immense amount of resources on their system for what?

Such kind of tech evolution must end or we will collapse soon digitally speaking.