I had exactly the same experience (minus reading the book). Often, I'd just see the function signature and no further explanation. I do realise that it takes a lot of time and effort to build up extensive docs, but it happened enough that I put it down and started looking for another Lisp that compiles down to a binary.
It feels like a lisp - just without the S-expression syntax.
Also, having Rhombus doesn't mean Racket is abandonned.
Far from it. Rhombus is built on top of Racket - and has
gained a few nifty features in the process.