> you better use a reasonably popular general purpose language

Most languages are horrible at templating, so that's its own world of pain.

What kind of templating are we talking about? HTML or in general?

If we take python, for example, you could use jinja for HTML and composition/inheritance for the general stuff.

That's all django does, and it does it well. I don't see what nix is doing so much better.

Prefer JS/TS? You can have JSX, which is superior in any way compared to this nix-based abomination.