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.

La issue nomina Next.js, React, SSR, CSR, routing e createElement, ma non identifica alcun file, test o punto di ingresso. Chiarisci innanzitutto se la richiesta riguarda il sito della documentazione di React o il comportamento di Next.js, quindi definisci una modifica alla documentazione specifica e verificabile prima dell’implementazione.