I had to google 'django magic removal branch' just because it sounded so cool:

https://code.djangoproject.com/wiki/RemovingTheMagic

I think your experience with Rails (and the community) may be a little out of date. Check out wycats' changes in Rails 3.0 to see where most of the cleanup happened. There's a lot less magic than there used to be.

As far as authentication and admin sections, I guess it just depends on your preferences for which pieces should be included in a framework and which users should have a choice over. Authentication is often app-specific enough that it's hard to drop in different solutions and have them act equivalently.