Too many bugs. Too many features rushed out the door. Every major AND minor version of NextJs has new features and/or breaking changes, which is fine on its own but existing stuff often also break.

We go through a cycle of: new feature -> patch fix -> minor fix -> improvement -> finally works -> replaced by something else OR it broke again.

For something like NextJs that has been running for years maybe more focus on polishing the existing features would be a good start.