My ISP is unlikely to be a problem. I literally get higher speeds downloading from servers across the world in Australia [1] than from CloudFlare's benchmark. Something around CF's side is funny, not mine.
I'm looking at the network tab, it seems like they send a ton of small requests instead of a large one... which might point in the direction of the problem.
[1] https://syd.mirror.rackspace.com/archlinux/iso/2022.04.05/ar...