[Philip-J-Fry]

AJAX took off because it's good for interactivity. If your "AJAX" requests are literally blocking the functionality of the website then they're no better than returning a big HTML blob. Your page just takes longer to load and the user experience is worse.

[arghwhat]

Returning new HTML blobs will never be faster than an equivalent AJAX roundtrip. In other words, if AJAX is slow when "literally blocking", fetching new HTML is at least that slow as well.

Static HTML only has a potential latency benefit on first load due to the ability to save render-blocking resource roundtrips. For later requests where those resources are already fetched, it only adds bandwidth overhead.