I'm open to the idea that we're doing it wrong and that there's a correct and pleasant way to write nextjs, but I think with the tools available today, everyone should just profile and optimize their app so they don't need to render it serverside.
TanStack Start absolutely merits a closer look. It's not a flash in the pan or "the new shiny". It's the robust, coherent, independent and logical evolution of battle-hardened wisdom and brilliant design and implementation from first principles. See TanStack Router and TanStack Query for more evidence and background context. I've been around the block (25+ years in webdev) and gained a deep appreciation for Tanner's way of thinking. No affiliation, just a grateful user trying to help others notice by amplifying the signal in the noise.
P.S. Yes I wrote ~"it's not X, it's Y". No I didn't use genAI to write here (nor anywhere, ever).
Perhaps this is where the core problem lies. Have you considered, that this obsession to leave servers and to try to unload all the work to the clients is the wrong way (for most sites)?