Very well written, the differentiation between a modified package and how to use it is what I would have needed at the beginning! Many examples directly throw overlays into the mix which makes it confusing IMO.
Thanks! Indeed, I had the idea the overlays (in combination with ~/.config/nixpkgs/config.nix) can be very confusing when overly used.
It requires explaining final and prev, which is hard on its own. In the manual they are called self and super, which is extra confusing. In general the alternatives should be preferred where possible.
This also does seem to be a bit of a trend. Longtime Nix users avoiding certain Nix features, while they are recommended by the manual. Overlays, nix-env, nix-channels, amongst others.