I'd agree, for 95% of projects. If you are serving web pages, or implementing something that doesn't have a lot of server side work in between requests, then sure, pick Rails.

But if you do have something active running on the server - ingesting something, holding connections open, talking independently to other systems, anything soft real time - you will very quickly run into the limits of pure web frameworks and will be forced to re-invent all manner of wheels and end up building much more than you need to. That's where elixir shines and is, IMO, the optimum choice.

Phoenix is basically "rails for when you actually need something more than build the world/destroy the world web requests". It's great for that, and those kind of projects are more interesting IMO, too. But for anything else, use Rails (or, yes, Django).