In my personal experience codebases using MyPy tend to be considerably worse than codebases that don't.
By using a static type checker on a dynamically typed language, you have admitted you don't know what are you doing right of the bat. This means the software engineers in the project are very bad and therefore the code quality overall will also be bad.
Tools like MyPy exist to make Python appear to be more like Java to help Java developers, who aren't willing to learn how to code in a different programming paradigm.
That code will always be far worse than Python code written using the Python development paradigms.
By using a static type checker on a dynamically typed language, you have admitted you don't know what are you doing right of the bat. This means the software engineers in the project are very bad and therefore the code quality overall will also be bad.
Tools like MyPy exist to make Python appear to be more like Java to help Java developers, who aren't willing to learn how to code in a different programming paradigm.
That code will always be far worse than Python code written using the Python development paradigms.