SSR is fine. We used to call it "PHP" or "Ruby" or "Java." People need to stop reinventing things, but feature development outweighs maturity when you have funding.
The stuff you mention was “born” at the backend and was then used to render frontend html at the very beginning then css, then JS etc…, but going from a frontend framework like React to the backend is an entirely different beast.
Because it denies people a chance to live in peace. If the ego constantly needs to justify itself, then we can't live in peace. If you need to learn, please do so on your own and bring what you can from your private learnings. It's not obvious to the rest of us why their framework needs such a security apparatus. The reason it's not obvious is because most of us don't see it as obvious (by definition, its not an obvious thing they are doing). Security, of all things, should be obvious to us all. As in, most of us should go "well this could have happened to any of us", but I don't think we are all thinking that. We are kind of thinking, "why would you confuse security to this degree across these layers?".