One thing not mentioned is the massive amount of complexity and difficulty involved in Starlark rules. In the next generation of build tools, I really wish Starlark could be replaced with some subset of TypeScript, which would have drastically better IDE support. And I wish the typing would be done in such a way that it's harder to do things that are bad for performance. Starlark is super difficult to read, navigate, and write, and there are a lot of performance gotchas.

I know there are efforts like starpls (language server for Starlark) but in my experience it really falls short. I think buck2 has type annotations but I kind of hate Python-style types, so I wish we could just use TypeScript :P TypeScript is even better positioned to fill this role now that tsc is being re-written in Go.