Aside from the obvious that ninja let's you use django.
The thing is, Django isn't just a web framework. Django is a CRUD app framework. It's great for building CRUD apps, but that's about it. In other words, it makes the easy stuff easy, but doesn't help with the hard stuff (in fact, it often hinders it).
I think the real reason for using Django is the "app" ecosystem. You wouldn't be able to get Django-style packages with Pyramid. It's possible with Django, though, because it's a CRUD app framework.
If you're not using "apps" then I guess the only other reason is the community support that you probably won't get from Pyramid + SQLAlchemy or similar.
You get all of that with any of Pyramid, Flask, FastAPI etc.
As for "pool of developers", I would expect any backend web developer to be able to pick up anything in a couple of days at most.
Yes, with fewer batteries, and so less consistency between projects, etc.
> As for "pool of developers", I would expect any backend web developer to be able to pick up anything in a couple of days at most.
Not some half-baked homegrown ORM, etc. Been there, seen it fail.