At one time quite recently, Cloudflare was on Spamhaus's "Don't Route Or Peer" list. Imagine where the world would be if anyone cared about that list.
But if an entire ISP is blocking you based on UCEPROTECT, which is designed for email spam filters - are you sure? An ISP that blocked all of DO would get so many complaints and be open to so much legal liability. Usually these are only used for email filtering.