I work on a reasonably large Django project (1M+ LOC) with approximately 100 developers and mostly have a reasonable time debugging. We use mypy, lots of linters (some custom flake8 plugins), and a fairly strict layered architecture[0] that's enforced with tooling[1].

Without the tooling it's a nightmare. My previous Django project with approx 500k LOC had linting and some typing and that was a mess.

[0] https://github.com/octoenergy/conventions/blob/master/patter... [1] https://github.com/seddonym/import-linter