I used the term "blocking" in a loose sense. I have no idea if Cloudflare was failing to resolve certain domains because it is a shitty service, or if it was ordered to block those domain names by its government, or if it was actively not resolving domain names because it thought a good idea to be a sort of arbiter and gatekeeper. I suspect the last option, but it is just speculation.
What I can affirm is that I had issues more than once with domain name resolution when I used 1.1.1.1. After it annoyed me enough I switched to Quad9, and it has been great ever since, which is why I recommend it as a user of their service.