Author of core.typed here.

I will challenge that schemas are "significantly" better for documentation than core.typed types.

With unions, intersections, heterogeneous maps, parameterised classes, recursive types we can be very expressive.

Here's some examples of the syntax for types: https://github.com/clojure/core.typed/wiki/Types

And some declarative types in action: https://github.com/frenchy64/core.typed-example/blob/master/...

I think core.typed is restrictive enough to allow annotations like the one above, while being opinionated enough to guide the programmer to write clear, comprehensible types.