Nothing against Cloudflare, but I don’t think it is good in general for the Internet that they are getting so critical. For them this sounds like a good deal (is money involved here?). Having more control of DNS should mean they can provide better service for their customers.
There is a lot of money involved. When you resolve DNS only over Cloudflare, all Cloudflare sites will have a much lower DNS resolution time than any domain that is not hosted by CF's DNS service. CF can also do geo DNS more efficiently, potentially saving millions in edge nodes.