I have no particular views on performance but the thing i keep hearing about next of 'this is solved by using one particular hosting provider' really surprises me as something people are ok with.
I think people reasonably expect, say, an aws lambda to be aws specific.
That's a very different story to React, which is supposed to be a library for general application ui development, and the official react documentation recommending Next as the way to use it.
I've been using React on and off since 2017 or so. Back in the day it was typical to bundle your React code and integrate it with the backend framework of your choice. It was stable and cheap. In the 2020s frontend tech took a bizarre turn...