Not crass at all. I would suggest that you follow your gut instinct. If NixOS excites you, go for it. If you want to understand the intricacies of Linux itself, look into Linux From Scratch. If you want to understand how “regular” distros work (and what sets them apart from each other) hop around between your usual suspects until you’ve scratched that itch long enough. Want to form your own opinion around init systems? Use a distro that supports Runit, s6 or OpenRC besides systemd.
I don’t think anyone else can tell you what you should do in this situation.