Template inheritance with blocks, as they do in Django or Symfony.
That way you don't have layouts anymore, but (usually) a base template that an action view overloads with its own content.
I know Ruby on Rails doesn't work like that so I guess that's why it didn't take in Phoenix (yet?).
Agreed. Once you're used to template inheritance it's hard to go back.
What is the modern model that you do use? Phoenix is very flexible and I'm wondering if it could easily be added manually.