I've been thinking about this a bit, and I think that the way forward is for Python to ignore the text of annotations ("relaxed annotation syntax"), not to try and make it available as an expression.
To be honest, the most pressing issue with annotations is the clumsy way that type variables have to be introduced. The current convention, `T = TypeVar('T')`, is both verbose (why do I have to repeat the name?) and widely misunderstood (many help request for mypy and pyright follow from users making a mistaken association between two type variables that are unrelated but share the same TypeVar definition). And relaxed annotation syntax alone doesn't solve this.
Nevertheless I think that it's time to accept that annotations are for types -- the intention of PEP 3107 was to experiment with different syntax and semantics for types, and that experiment has resulted in the successful adoption of a specific syntax for types that is wildly successful.
I don't follow your reasoning. I'm glad that type hints have found success, but I don't see why that implies "and therefore we should restrict the use of annotations solely for type hints". Annotations are a useful, general-purpose feature of Python, with legitimate uses besides type hints. Why would it make Python better to restrict their use now?