I'm a bit surprised to see that you disagreed with the "NixOS is hard to configure" bit, but then also listed some of the reasons why it can be hard to configure as cons.

By "configure", they probably didn't mean just setting up say, user accounts, which is definitely easy to set up in Nix.

The problems start to arise when you want to use something that isn't in Nixpkgs, or even something that is out of date in Nixpkgs, or using a package from Nixpkgs that then has plugins but said plugin(s) that you want aren't in Nixpkgs.

From my experience with NixOS, I had two software packages break on me that are in Nixpkgs - one of them being critical for work, and I had no clue where to even begin trying to fix the Nixpkg derivation because of how disorganized Nix's docs can be.

Speaking of docs inconsistencies you still have the problem of most users saying you should go with Flakes these days, but it's still technically an experimental feature and so the docs still assume you're not using Flakes...

I was also working on a very simple Rust script, and couldn't get it to properly build due to some problem with the OpenSSL library that one of the dependent crates of my project used.

That was my experience with NixOS after a couple of months. The concept of Nix[OS] is fantastic, but it comes with a heavy cost depending on what you're wanting to do. The community is also great, but even I saw someone who heavily contributes to Nixpkgs mention that a big issue is only a handful of people know how Nixpkgs is properly organized, and that they run behind on PRs / code reviews of Nixpkgs because of it.

I'd still like to try NixOS on say, a server where I could expect it to work better because everything is declarative such as docker containers - but it's going to be a while before I try it on my PC again.