I just started a new app, and I decided to try Phoenix LiveView. It's really simpler and easier to work with. It won't work well with all kind of apps, especially those with offline support, but for many many apps/website it is a good fit.

The last app I did was a mobile app written in Elm with Phoenix. I can't recommend Elm enough, it makes JS much easier to work with. For communication I used a simple REST oriented API.

While I understand why GraphQL exists, I think it is a major addition in complexity for little to no benefits. I tried it, wrote half a project with it, but they removed it. When things gets complex (for example, let's say the user.email field can be redacted under some conditions) your endpoint becomes really hard to manage. GraphQL certainly have a use for large API with graph oriented datasource (well, like facebook), but it is a specific use case.