Having done a py2 to py3 migration and ran into the same issues, these wouldn't of been that big of a deal IF python had static typing from the get go.

The static compiler would notice all the breaking type changes at compile time and you can systematically fix all of them at once. You wouldn't miss one or two and have to run your unit testing suite to exercise the type system underneath.

I really believe big breaking changes like this in a language causing migration stagnation is a property of dynamically typed languages. With other statically typed languages like swift or rust, it happened quite frequently but wasn't as big of a deal in practice.