There is some good work going on for the lower level pieces:

https://github.com/anmonteiro/ocaml-h2 - HTTP2 stack

https://github.com/inhabitedtype/httpaf - HTTP stack

For micro-frameworks there are a few options available like

https://github.com/rgrinberg/opium

https://github.com/ostera/httpkit

There are some scattered pieces in the ecosystem for routing, sessions etc but i agree that compared to Python, JS, etc the ecosystem might not look as cohesive or expansive for web applications. So there should definitely be room to have new solutions in this space