Almost every point being made in that comment grossly misrepresents the facts and/or leaves out key details. For specifics see this comment[1].

If you're curious about Nix, I highly recommend you give it a try. nixpkgs have great quantities of packages that matches Arch/AUR, and every single one of them goes through mandatory reviews ensuring quality. On top of that, the Nix tooling makes it easy to create your own packages and reuse existing package definitions. So for example, if you want to use a fork of a software available in Nix and maybe even add some custom patches, all you need to do is write a few lines in your config. Switching to Nix was a really refreshing experience and the amount of documentation and the code in the nixpkgs repository was very helpful for me to get started.

[1]: https://news.ycombinator.com/item?id=25030546

Plenty of us do use it on our own machines and in production, and it doesn't seem like a never-ending packaging war.

Most software actually doesn't assume the FHS. (Autoconf, Meson, and CMake all don't, for example.)