>And yet it's somehow being pushed as a be-all solve-all replacement
But it isn't a be-all solve-all replacement. The whole point of HTTP/3 is that you can still use HTTP/2 all you want in your build-outs, and it uses as appropriate. If large file, many packet, high speed sustained performance is your thing and you've got problems with HTTP/3, deploy it on an HTTP/2 server. Go nuts. Positively nothing will go awry. Everything will be fine.
You're arguing a strawman.
>Additionally, if your performance degrades even in these ideal conditions, what does this promise for non-ideal conditions?
This is an absolutely nonsensical statement. HTTP/3 is quite literally built for situations where you have many small requests, often in suboptimal situations. The average web user interacting with an average web page over something other than their local ethernet connection, exchanging tens of thousands of back and forths for different resources and navigations and posts. Screeching, with moral superiority I might add, that if it pins the CPU using their oddball no-name server -- oh, and where they bizarrely forced the HTTP/3 server to use HTTP/2 congestion control because that made the results funner -- with their client machine with a CPU 1/4 the performance of my smartphone, downloading a many GB file, isn't the big win you seem to think it is.