As others have said, mix phx.new --no-webpack. Our choice to use Milligram as a tiny, unobtrusive css file is an odd hill for you to plant your phoenix-is-turning-into-a-nightmare flag on 
Seriously, we previously included Bootstrap as a sane default, which required us to pollute our generated markup with bootstrap specific classes. I didn’t think this move to pollution-free markup would be controversial.
At any rate, it’s clear you care about Phoenix, and I appreciate that, but rest assured, focusing on a nice up and running experience for on boarding newcomers is not going to ruin us – it’s the key to our continued success 
cant wait for it, awesome relesase nevertheless