But there is a different use-case, when you've data which is public but logged in users see the content customised or more capabilities.

Agreed, I just don't usually work on apps that have this component.

Also, I think the nextjs/blitzjs zero API approach is somewhat novel (and I assume this is what people like the most), but it goes against my general lack of enthusiasm for isomorphic applications. I think inertia.js is a nice technology agnostic approach to achieving similar goals though.