You linked their DNS server, which is not their proxy, but yes I use both.
Cloudflare often comes under fire for privacy concerns, but that's literally true of every public DNS server out there. No one can feasibly run their own DNS server at home. Those requests ultimately have to go somewhere.
I don't use Google's DNS server, because their business model relies on their ability to spy on you. Cloudflare's business model relies on providing reliable network services, and maintaining public trust. In addition, the scale of surveillance they would have to do with the volume of requests they get per second is entirely unfeasible. They simply have too much data flowing through their servers for it to be reasonable.
Could they be spying on me? Yes, but so could anyone, and among the options, they are the least motivated to do so.