A Javascript backend is better focus than one usually sees. There are also quite a few web dev projects in the nimbleverse, and https://forum.nim-lang.org is written in Nim and there is much support code in the Nim stdlib.

Frameworks/simplifications are better left to the broader community that knows their own web-needs. It took many years for things like Django for Python or Rails for Ruby to appear. Even now, those are not part of the respective core languages, but external projects.

Anyway, it's open source. Instead of just wishing for more effort, adding your own effort might be even better! :-)