Currently trying to modernize a python project that doesn't use modules, just executable python files that import each other with custom sys.path hackery, which is also used for globals, no type annotations, GLib used for everything including math and string to int parsing.
In my defense, I had to hack around a different Python library also manipulating sys.path, which nobody likes except this one dev team in a different timezone. They somehow got a director to declare that I would fix this issue they self-created before they woke up in 8h, and I wasn't allowed to rip out the library. So, ugly sys.path manipulation in the exact way that library wants. Not proud of it, but it sounds like you were given time to engineer an actually correct solution.
I can fully see how and why this might have grown historically in ye olden days of python2, but it's not sustainable to continue adding floors ontop of a rotten foundation. Code needs maintenance like anything else, and far too often there's no budget or time available for it. Even if that maintenance would reduce the overall workload.