http://crimeflare.eu.org list reasons why not to use Cloudflare, though IDK if it's just ultra-privacy oriented warnings or something else...
Not sure if I should be upset, although the claim of CF potentially sniffing passwords/credit card details/other sensitive information across various websites sounds plausible to me (some websites even have a TLS cert verified by "Cloudflare, Inc."!) 🤷♂️
You had me until you mentioned blockchain technology. How would a blockchain system help in that regard, anyway?