I have used next in a pretty large application. Also built decently large things with base react (vite), vue (nuxt). Also small stuff using other platforms.

Next is by far the worst thing ever. Everything is broken in a weird way and the deeper you dig into it deeper it starts biting back. It was the only thing I dreaded maintaining.

Now that LLMs write code, it probably is not be as big of an issue though.

Still would not wish next upon any of my enemies.