I don't see how this is any different from jquery style development from eons ago except instead of jquery you now use react components that can SSR a nonempty

I don't see how this is any different from jquery style development from eons ago except instead of jquery you now use react components that can SSR a nonempty initial state. Which you could do before too, few people just cared enough to do the extra work. Seeing buzzword labels on every little variation of age old techniques every other week is exhausting. This "Islands Architecture" is pretty much what everyone was doing before SPAs came along.