Type hints are not Pythonic. The syntax is ugly. It adds "stub files", like C's ".h" files, something newer languages such as Go and Rust don't need. Some of the proposed syntax is even in comments, because it didn't fit the language. But something had to be done to meet competition.

The problem Python faces is that Python's Little Tin God painted the language into a corner. He insisted for years that everything in Python had to be fully dynamic. This limited performance.

Then came competition in Python's space. Go came along, Javascript got traction on the server, and Python faced a real threat. Both of those can beat Python on performance, sometimes by huge margins, and they're useable by Python-type programmers used to the freedoms of scripting languages.

The Python 3 debacle had already thrown the Python community into disarray - most of the production work is still on Python 2, which was supposed to be abandoned but refused to die because the cost of conversion was much higher than expected. Meanwhile, Python 3 takeup was far less than expected; numbers like 10-20% come from downloads, and production use is probably less. Another incompatible change in the syntax would be rejected by the market. An incompatible change to a "typed Python" wouldn't fly.

So we get PEP 484, which is ugly but might help Python survive. Might.