I often read that Next.js sucks. Meanwhile I and many other devs I've spoken to IRL find it does what we need it to do without any issues. Ya'll just some haters.
For all my criticisms of it, I built two commercial apps in it. I worked around the issues and it was fine.
I've also built commercial apps in other stacks and they also have their warts.
What I've noticed from the other stacks, however, is that the frequency of entirely unnecessary issues is simply lower. React and NextJS aren't going anywhere and one can hope that these things will improve over time.
Ultimately, it's also a great employment guarantee, as companies will need people to maintain the apps that are constantly changing.
I think applying scepticism to Vercel and its motives is healthy, still.
See the various other comments for concrete examples of why nextjs sucks and the team at vercel is incompetent when it comes to auth, middleware, caching, and just generally maintaining a usable framework without brutal migrations and api breakages.
They have made egregious mistakes that go far beyond "move fast and break things" and well into "we should have the lawyers join this call".