I like the concept, but honestly I don't see myself writing an entire webapp with this.

Here is some feedback:

There are a bunch of libraries that need to expose an http API. There is a niche for providing an embeddable http server that comes batteries included with all the features such as rate limiting, authentication, access control, etc. Things that constantly have to be reimplemented from scratch, but would not warrant adding a large framework by themselves.

That's where I think the idea of a "WebDSL" would shine the most.