Can you elaborate what you mean by decorative?
If you run a type checker like ty or pyright they're not decorative — you'll get clear diagnostics for that particular example [1], and any other type errors you might have. You can set up CI so that e.g. blocks PRs from being merged, just like any other test failure.
If you mean types not being checked at runtime, the consensus is that most users don't want to pay the cost of the checks every time the program is run. It's more cost-effective to do those checks at development/test/CI time using a type checker, as described above. But if you _do_ want that, you can opt in to that using something like beartype [2].
[1] https://play.ty.dev/905db656-e271-4a3a-b27d-18a4dd45f5da
Exactly my point. If I need to run 300 external tools for a language feature to be worth a damn, why is it a language feature?
‘uvx ty check’ or ‘uvx pyrefly check’. That’s hardly 300 external tools.