I'm replying to your post, specifically, but the other comments seem to be making the same point: HTTP2 confers a performance advantage.
So I repeat my question: is this speed advantage stricto-sensu necessary? Why can't one "just" spin up a few more EC2 instances until this is fixed?
Is there a case in which HTTP2 is necessary, and HTTP1 just won't cut it? I think that's the sense of the original question, and I think it's a valid question when talking about hacking one's way around bugs that are going to get fixed anyway.
I'm open to being wrong about this, but I'm surprised at the resistance to this question.
I'm not really sure that kind of comparison makes much sense.
HTTP is a layer 7 protocol, IPv6 is layer 3. Rolling out a layer 3 change is an entirely different thing and requires not just the two parties using it to be adapted, but everything and everyone in between. That plus a general lack of a positive business case for v6 has meant tremendously slow adoption.
HTTP/2 support on the other hand has been quickly added to major browsers and with a number of big players like Google and social media providers supporting it those numbers would rise much more quickly. Cloudflare and similar providers would skew those metrics too since they can accept the connection over HTTP/2 from your client but still talk 1.X to the backends.
There are quite a few studies that show that revenue drops proportional with performance, i. e. if people have to wait 4seconds instead of two, you're leaving half your revenue on the table.