It is a batteries included _front end_ framework. You don't need to worry about compiling, routing, code splitting, etc. Most of the things you described should be handled by the back end service
From the first page of Next.js docs: "Next.js is a React framework for building full-stack web applications"
> You don't need to worry about compiling, routing, code splitting, etc
IMO that's the least you'd expect from a web framework.
Meanwhile.. last I checked you still had to choose how you were going to roll your own auth in rails. Are people not often just installing bcrypt and adding a users table with their password hash? Or is there a generator for all that now?
Anyway, I disagree with the idea that Next is Rails-like. Adonis is probably still the closest in the JS/node ecosystem, though Redwood might also serve a similar niche for the types of apps it works for.
Next and the other "frontend metaframeworks" (as they're called now), are certainly much closer than the most popular choices 7 or 8 years ago (often cobbling together React and Express and an ORM like Prisma, making a bunch of other decisions, and then doing a bunch of the integration work by hand)
Also Rails only recently got authentication. For more than a decade you needed Devise or something else.