Yes, all libs give you vendor lock-in, which means unless Next is a particularly egregious example, there's not much point calling it out as a particular wart. My argument is that it's closer to the opposite, because as far as web frameworks go, Next does this better than most -- very little of the code you write is different just because you're using Next, your code is just normal React code. This is a huge contrast to something like Gatsby, where the lock-in is much stronger.