It's the other way around. The site blocks Cloudflare for some political reasons that have been mentioned here before, but I can't remember what they were.
I thought it was because Cloudflare DNS doesn't pass on the full IP subnet of the requesting computer, which archive.is wants. archive.is says they need it for better CDN routing, CloudFlare says it's a privacy violation and there are enough CloudFlare PoPs to provide for CDN granularity just by going off the requesting server.
