Can you expand what you mean re: large projects in Python?
I've been a happy Python programmer for over fifteen years, so this comes from a place of love and respect.
Beyond roughly 150k LoC you start to run into difficulties keeping everything straight over time, especially if you use a lot of indirection or other magic. The aspects of the language that help you go fast when you're prototyping (is "RAD" still a thing? Rapid Application Development) start to trip you up when the codebase matures. There are a lot of fancy footguns in Python that catch you if you stop dancing.
Tooling is getting a little better (MyPy, et. al.) but at the same time the overhead of adding explicit type information erodes the advantages Python has over, say, Java or Haskell.
There was at least 1 really large error that slipped into production because we were mocking an untyped service incorrectly (a mistyped property name), and the test passed, but prod exploded. It was embarrassing, and I certainly would have caught it with more mypy discipline, but overall the pros outweighed the cons.
At big companies that use mypy, however, this is problematic. If teams only define types for the straightforward parts of the system, then the types become less useful, especially as the company scales. From what I’ve seen, individual teams use an all-or-nothing approach with MyPy, so it’s unusual for an individual dev to sparsely type anything.