If you are spending "days" in some Django Admin modifications, you are definitely doing it wrong. At that point you should have rolled out your own admin just like any other feature. Clearly the builtin admin is working against you rather than with you if it takes that long to do what you need to get done.

The Django admin is meant for development. Ofc, it can be used by non-devs and I've seen a multimillion dollar business that mainly uses the builtin admin to manage their main product. However, there's always that point when customising something that is fundamentally different than what your needs are doesn't make sense.