I tried Next.js very briefly and I initially found this concept really nice. However I bounced back and gave up on the framework for some related reason. I felt like I gave up control to much, maybe due to the routing model. Feels like some common problems were made much harder because of it.
I implemented it in a bookkeeping app I’m working on. It works nicely but the documentation is very poor; I had to constantly refer to a third party example.