One can observe that even the proposed alternative is still awfully complicated compared to the web apps I remember making circa 1999. Much more capable, but still more complicated. Of course the entire "typescript -> compile -> minimize -> pack -> etc." pipeline is yet more complicated.

There is some essential complexity that will arise in this space because a client/server app fundamentally can't abstract over the client/server division. There's not much you can do about that... well... you can overabstract and try too hard to wipe it away, and fail, and make something that will be worse to use than an approach that acknowledges and understands the distinction, which is a modestly popular approach... but there's no way to get rid of it entirely.

There is some complexity that is going to be essential in an app context where the DOM is not exactly the best API for interacting with an application, and there is always complexity where there is an impedance mismatch.

Those two things alone are non-trivial on their own. Exactly how much they account for the complexity of the current approaches is up for debate, though.

At the risk of incurring some ire in replies, it's not clear to me that if someone sat down with a clean sheet of paper and tried to create a new platform that roughly matched the current web platform in capability that they could do that much better. There's a lot of deprecation that could be trimmed off for sure, but perhaps for the purposes of this discussion we wouldn't count that against the current platform too hard. (The new platform will only be missing it by virtue of being too young to have it; over time it'll pick it up too.) Maybe building in some sort of reactive-programming capability at the base. A better version of web components that works well enough to be the de facto standard and prevent too much competition from emerging. But whatever data structure you use to access your app, it's still going to have roughly the complexity that we have today. You could do some better. But I'm not sure you could do that much better, such that it would be heaven compared to today. It's still going to be huge and complicated and have all sorts of weird interactions when you try to put the pieces together.

Trying to build an app in a language that is also trying to be a high-powered layout language (it's not the best, not exactly "commercial quality", but it's pretty capable) that is also a document standard that is also the de facto VM for the world is not going to be simple.