Any company that's 10 years old will have code that's 10 years old in every language they use. And every language has some flaw that was "fixed recently" but that's not relevant in a mature codebase. Like "Python packaging is fixed now with uv" no it's not. And especially anything to do with threading vs cooperative multitasking will stick around.

Mostly old code will keep working, but there are exceptions like Python 2->3 breakage that deserves all the criticism it got.

Yes and with Java they’re the ones still prioritizing annotations over the options built into the core language.