It doesn't help that US diverging diamonds seem to insist on having pedestrians walk through the median.
But honestly all interchanges are varying degrees of horrible and if you want your city to be bearable to navigate as a pedestrian/cyclist you just really don't want to do urban highways, or roads above a certain size in general.
The matter of flakes is complicated. Yes they are experimental, but in reality most Nix users use them despite that. I'm a bit on the fence on whether you should start with flakes because they do add some complexity. You can copy paste a sample flake configuration from the Internet (there are many but they all do exactly the same things) and you'll probably be fine but telling people to just copy paste code they don't understand feels wrong as well.
Regarding documentation... I wouldn't go as far as saying you should avoid it entirely but it is in a very unfortunate state with a lot of wiki pages being outdated or just containing snippets that do things in very weird ways, or are over engineered to the point of being incomprehensible.
And that's if someone bothered to write up anything at all. It's a bit sad but reading from the nixpkgs GitHub (or other people's dotfiles) is sometimes the only way to get certain information, such as valid values for package overrides.