Yes, gmail might have had some SPA-like behaviour in 2004-2006 but it was nothing like what we have today. Pretty sure I got access in 2005 because I knew someone who worked at google, and it was mostly doing full refreshes between actions at the time, like pretty much the entire rest of the web
You seem to be trying to redefine SPA to mean something else and much vaguer - the use of some specific frameworks, or not being "hacky" whatever that means - but your history here is just off. Reality is the web has changed relatively little since 2008. It got some more APIs that weren't new, they were used in native desktop/mobile apps for many years beforehand, and that's about it.
SPAs certainly were a thing back then, it was just called AJAX. (Not to mention the desktop apps that were, architecturally, almost the same thing.) jQuery was a response to the popularity of putting interactivity in the browser, not a precursor.
The questions remain the same, not just from 2008, but going back a long ways… Where does the code live? How is it transformed to execute, where does it execute and how it is moved there? Where does the data live, how is it transformed and moved to where it needs to be displayed, and how are changes moved back? When some of the answers shift, due to changing network capabilities, processing capabilities of nodes, or scaling needs, it’s doesn’t really change the overall picture.
Or typescript! I was writing actionscript 3 in 2008 which is essentially the same spec
I'm sure there's still room for innovation, but I think a lot of it going forward will be driven by rapid improvement in AI capabilities.
In 2008, tech wasn't everywhere. iphones were brand new and very few people had them.. There was no "mobile browser" market share (though we did have SMS gateways). 77% of the global population hadn't even been on the internet yet.
AI looks like it's going to be at the forefront of the next big wave of fundamental changes to society, and it's really hard to predict where that will lead us. But I suspect it's going to become apparent that this relatively brief period of tech-elite empowerment was a historical anomaly, because the AI underlings are going to be willing to do a lot more work with none of the coddling, and they're going to improve very quickly.