Third party tools (mypy, pyright, etc) are expected to check types. cpython itself does not. This will run just fine:

python -c "x: int = 'not_an_int'"

My opinion is that with PEP 695 landing in Python 3.12, the type system itself is starting to feel robust.

These days, the python ecosystem's key packages all tend to have extensive type hints.

The type checkers are of varying quality; my experience is that pyright is fast and correct, while mypy (not having the backing of a Microsoft) is slower and lags on features a little bit -- for instance, mypy still hasn't finalized support for PEP 695 syntax.