Next.js is easy peasy and lovely and wonderful until you need to mix in validations + translations + authentication + authorisation + calling upstream APIs with user's credentials + ...
That's when you realise using what would be a perfect framework for building landing pages might not be the best one to build a full web application.
Isn't that the part where you as a developer step in? Most of these things are solved problems with mature libraries to integrate. I much rather mix and match then fight some all-in-one super framework that doesn't do quite what you need.
I think my job is to ship useful, secure and robust features to my company's customers. Dealing with technology is a consequence of that, not the end goal itself, which seems to be what's most wrong about this industry.
Certainly tying together libraries (or writing your own framework) is a valid approach, it's just a lot more expensive to reach the same quality level. That's why usually you end up with half assed solutions or never ending projects.
That's when you realise using what would be a perfect framework for building landing pages might not be the best one to build a full web application.