There have been plenty of new backend approaches since the term Web 2.0 was minted. The important change was a shifting from one request per view to multiple requests that comprise a view: it was the client/server interaction patterns that were important.

The fact that you build your “web 3” application using Web 2.0 techniques (SPAs, etc) tells me that web 3 is not a thing. It’s another type of backend, and the web is designed to have those appear in perpetuity.