Full-stack is an overloaded term, but it used to mean "a completr solution for building a web app."
From the comment above: Next.js is the opposite of a "batteries included" framework. No abstractions for ORM, background jobs, sending emails, managing attachments, web socket communication - all very basic stuff when dealing with a production application.
Well, if you went so far as to reimplement Next.js, I don't think you're using Rails either.
And frankly I'd like to see it since that's a really hard problem to just roll your own solution. And probably a huge waste of time if you're trying to ship a real product on top of it.
Linear was started on next.js? I thought they built a custom sync engine? https://linear.app/blog/scaling-the-linear-sync-engine
I feel like this article is hyping up the importance of next.js.