More modular? I think how modular it is, is one of Django's greatest strengths. Don't like django's templating? You can be up and running with jinja2 in less than 20 lines. Don't like Django's user model? Substitute your own, or if you just need a different auth backend, write your own. Have a desire to use a less common DB? Write a db backend. As far as trashing the ORM for SQLAlchemy, there are a number of django packages that aim to do just that.

There is a small number of ways I could imagine Django being MORE modular.