1 URL = 1 resource
Right now, in every web browser that exists, there is still a so-called "address bar" into which you can type exactly 1 address. And yet, for a system that uses WebSockets, what would make more sense is a field into which you can type or paste a vector of URLs, since the page will end up binding to potentially many URLs. This is a fundamental change, that takes us to a new system which has not been thought through with nearly the soundness of the original HTTP.
Even worse is the extent to which the whole online industry is still relying on HTML/XML, which are fundamentally about documents. Just to give one example of how awful this is, as soon as you use HTML or XML, you end up with a hierarchical DOM. This makes sense for documents, but not for software. With software you often want either no DOM at all, or you want multiple DOMs. The old model was:
1 URL = 1 resource = 1 DOM
Perhaps the most extreme example of the brokenness are all the many JSON APIs that now exist. If you do an API call against many of these APIs, you get back multiple JSON documents, and yet, if you look at the HTTP headers, the HTTP protocol is under the misguided impression that it just sent you 1 document. At a minimum, it would be useful to have a protocol that was at least aware of how many documents it was sending to you, and had first-class support for counting and sorting and sending and re-sending each of the documents that you are suppose to receive. A protocol designed for software would at least offer as much first-class support for multiple documents as TCP allows for multiple packets. And even that would only be a small step down the road that we need to go.
A new stack, designed for software instead of documents, is needed.