> If Hack then really is a different language and you don't like PHP, why not migrate to something completely different?

For server-side web programming, what shall one adopt?

Python and Ruby are great dynamically-typed languages, with rich ecosystems, but don't have any type system. This makes maintenance, and evolution of the codebase, tricky in the long run.

For languages that do have type-systems: Go's is a bit too simplistic, while Java/Scala have robust type systems but are rather slow and don't hit the programmer workflow sweet spot.

There's no silver bullet around.