You’ve basically identified the advantages and disadvantages of Nix properly.
When you learn Nix and how it works, it is incredibly powerful. Being able to version your entire OS with one configuration is incredible. Old software that messes things up just doesn’t exist. It’s easy to explore new software, configurations, and upgrades and roll back to your old state seamlessly. No more “well I deleted an environment variable and now my performance is 50% worse and I don’t even remember what that environment variable was named or where it should live.” With Nix, you can switch from i3 to Hyprland, try it out for a day, and then switch back to your old configuration seamlessly and easily.
The disadvantages are that you need to know Nix (the programming language and configuration file syntax) to do it, and they are complicated. Worth it in my opinion but it’s not easy.
Every other distro is basically different from Nix because of this, as you will be configuring them manually to a greater or lesser extent. I find that manual configuration to be annoying and I always had to create tools to help version my configs properly before Nix. But it is certainly easier to do since you just have to understand the software you’re installing and how to configure it. In Nix, you have to understand both that, and Nix.
I think it’s totally worth it. But only you can make that call for you.