You don't need "a whole lot of JavaScript", though. React and Redux are under 100k minified. So, yanno, a Retina-doubled JPEG or so. Your own JavaScript need not be particularly large--we're talking text, here, and even text that gets gzipped over the wire. If you're dealing with 2G connections, I can see an argument. If you're not, repeating it for a page blank on every action strikes me as, er, significantly worse.
And, FWIW, I have been party to metrics and user experience that shows that 200ms of latency can double your bounce rate. That 200ms of latency is not going to be coming from downloading react.min.js.
You may be right in some niches, but overall what you describe does not square for applications I build nor applications that my clients build, and I've been doing this pretty broadly for awhile.
The cost is not transmitting the js by wire, but executing it. 100k of js is very CPU heavy.
SSR does help though. But then there's this whole rehydration...
As I said in a prior comment, YMMV and some people love it. What you're saying right now does not ring true for me. But I'm not the kind of person who likes to pressure developers on how they perform their craft. I was just sharing my experience since you seemed to be in doubt about whether or not I was making it up. I'm not.
> React and Redux are under 100k minified.
Of course. But you're paying the round-trip on every page request, you're page-blanking every time--it just feels worse. For some things (where you expect documents--a news site or whatever) that's not the worst thing in the world, but the modern web is increasingly less document-based and more application-based.
And if initial payload is truly that much of a concern, Preact + Redux is under 5KB minified/gzipped.
If the process of loading a new HTML page takes less than 300 ms or even 500 ms, it's negligible in terms of UX. It's easy to achieve this on a traditional site, especially if you use caching.
I may be cynical about it due to my own experiences, but I do not like SPAs anymore. You pay for a highly contextually specific increase in perceived performance with a lot of problems in unexpected places. Happy to go on and on about it if you like.