Lack of built in user authentication kills this project for me, that's just something I don't want to deal with building my own anymore after django.

ueberauth is one of the most fully featured with support for a ton of different authentication schemes (https://github.com/ueberauth/ueberauth)

But there are lots of other things that integrate with Phoenix / Plug (https://github.com/h4cc/awesome-elixir#authentication)