The Django ORM and DRF autogenerated views are very good for quickly building CRUD APIs.

You get a lot of stuff in the box with Django:

* a very functional (if exceptionally complicated and hard-to-modify) admin UI

* a friendly ORM with good support for autogenerated DB schema migrations (better than SQLAlchemy for simple CRUD, but harder to go off the beaten track when you need to)

And building on that, DRF gives you

* Autogenerated CRUD API endpoints for your DB models

* Autogenerated serializers for your DB models, with field type validation

All of the above exists as plugins for Flask, but the feature set is less well integrated, and you need to figure out which plugin you want to include.

If you're trying to build a super-light microservice then Flask is probably worth looking at, though you can get Django quite light with a bit of work.

If you're trying to build a more complex system with nested API endpoints then DRF makes this harder for you (it's not possible in native DRF, but there's a plugin for it; I'm using this approach so it's not terrible).

And if you don't buy in to Django's ActiveRecord ORM approach (e.g. you want to do DDD and want to use a DataMapper style interface on your DB), then you need SQLAlchemy, and you can't use all the clever ORM mapping tools that Django/DRF brings, and so you may as well use Flask.