Ask HN: What is wrong with jquery and server side rendering web pages?

I have been programming for the web over 3 years now mostly in asp.net, as a "full stack" but I honestly care way more about the database and the back-end that I do about the front-end

I think razor + jquery is usually good enough to make even complex pages. If I have to take care of a lot of variables maybe I use knockout.js. But that's it. Lately I was reading about react/vue and the SPAs where the routing and everything that I do so easy and well with the back-end is now in the front? and they are supposed to completely replace razor? what is the improvement for me as a dev to replace razor or use an SPA approach?