This is the thing people who haven't run a Rails app for years don't appreciate. I went through the Next.js pages router to app router migration on a production app. That wasn't a version bump, it was a rewrite across a different mental model.

Rails upgrades are painful but the path is documented, the deprecation cycle gives you a full minor version to fix warnings before they become errors, and the team usually knows where the sharp edges are.

The Ruby version management story is actually solid too. rbenv/asdf pin files make it hard to accidentally run the wrong Ruby version, which removes a whole class of environment drift issues you don't even realize you have until you've fixed them.

Switching from Next's pages router to app router (RSCs by default) is a major shift in architecture, practically replatforming. Not to be taken lightly (and an opportune time to consider less-opinionated modern alternatives, like TanStack Start).