Cisco at least release some low frequency summaries of the data they are able to collect: https://s3-us-west-1.amazonaws.com/umbrella-static/index.htm...
What legitimate uses would those be, and how is DNS involved in DoS mitigation?
Same goes for GeoIP — EDNS Client Subnet was specifically created for effective and cheap GeoIP. (BGP anycast isn't cheap.)
I mean, both issues are exactly why archive.is had to put the block in place. For sure both of these usecases are pretty legitimate.
BTW, what's the actual legitimate need to block ECS? After a domain name is resolved by DNS, you still have to connect directly to the hostname by an IP address, and your IP will be leaked — there's no way around this, that's how internet works. Cloudflare knowingly runs these marketing campaigns trying to obscure this simple fact that easily invalidates the need for their services, and invalidates the benefits of their service compared to competition.
The business case to collect DNS statistics is clear and imminently useful to numerous people and organizations, it's the complete lack of honesty about why they offer the service that bothers me.