Question about nextjs..

After using nextjs, the page movement time is very slow. I know React pushes nextjs, but when using react, I moved the page right away, but in nextjs, it feels like it moves too slowly. I doubt if ssr is the best. I think that csr should be selected separately or a better alternative should be created.
And there was a time when a custom was needed at the time of the route, but this is too internal, so it is a problem how to set it up. This developed an in-depth custom route according to the customer's requirements, but in nextjs, there are times when you can't get a sense of the implementation direction. What I'm talking about is customization. It's best to keep this as open as possible.
I use createElement and croneElement very usefully, but I was embarrassed to see that they were registered as legacy on the new React page. This is very useful for free customization.

The issue names Next.js, React, SSR, CSR, routing, and createElement, but it identifies no file, test, or entry point. First clarify whether the request concerns the React documentation website or Next.js behavior, then define one specific, testable documentation change before implementation.