> I could believe that type systems aren't particularly strong as an anti-bug layer.

They're absolutely huge for this, but you have to write code to take advantage of the guarantees that the type system can offer.

As Yaron Minsky at Jane Street put it, "make illegal states unrepresentable". Stronger type systems make it possible to make more states unrepresentable. You end up with what amounts to static debugging - you debug your code at compile time.

Sure, it's still possible for runtime bugs to occur, but entire classes of bugs are eliminated, plus it becomes possible to have static assurances about program states about things that most language don't even try to express in the type system, like security.