Yes, they can be written in maintainable ways, I didn’t disagree in my original comment. That doesn’t change that most of the projects I come across to this day are absolutely unmaintainable messes. I’m not talking about Python from 10 years ago, I’m talking about the projects I encounter now.
The biggest issue is that you have to limit yourself to a mostly non-dynamic subset of Python if you want type checking etc. to work, and you have to write your own type definitions for many dependencies. Most projects don’t do that, they instead lean into the dynamic nature of Python, which makes them unmaintainable after little time.
Many developments over the last few years have been for improving those aspects, e.g. Wayland is far more secure than X11 could ever be. There will be more vulnerabilities found, but it won’t be as bad as one might fear.