Yeah I've heard that before, but from my (admittedly brief) time it seemed like you could just use the utilities you want and ignore the stuff that forces you into a CMS'y box. Feels like if you really wanted to you could just use a form/serializer to validate input data and to return a domain object, pass the domain object to a service layer, and then use the django orm (or honestly anything if you really want to stray from the django way), to handle database interactions. I understand flask might be nicer because you get to feel like you dont have a bunch of wasted code bloat in your deployable, but there are some pluggable systems that come with django that are nice (user system, pluggable authn/authz, caching framework, etc.) I didn't really mind the bloat because a lean deployable isn't that important to me and it all felt sluggish to me compared to .net core anyway.

Yes you can definitely pick and choose the parts of Django you want. Sometimes they have interdependencies but you don't need to use it all. Or for example, use Jinja instead of its templating system