This. That customer of mine started a project a few years before hiring me. They used inheritance and each model is scattered around a number of tables. No external tool can sensibly access that database, except that very Django app and its manage.py commands. Add a similarly enthusiastic use of apps under the same main directory and the database is a mess of long named tables with a tangle of relationships between them.

We started another project later on and we planned the database first. We wrote one model per table, no inheritance, only a few cleanly delimited apps. We still use makemigrations and migrate but if we want we can write a piece of software on any language to access that database.