Next.js is really great, and has definitely helped push the industry forward. I'm not a fan of the way they handle routing, though, and we need to be able to evolve Redwood without fighting against our dependencies. If I had to guess, we may end up writing our own versions of other things as time goes on. We're all about integration, and sometimes you have to own things yourself to make it all work as seamlessly as possible.
FWIW we use Next.js without the pages folder convention, we use a routes.js and just have the pages folder as a build artefact, then we have relatively seamless integration with Relay to make data management super straightforward.
