Hence the need for Cloudflare?

Except that's exactly what you should do. And if they refuse to cooperate you contact the network operators between them and yourself.

Imagine if Chinese or Russian criminal gangs started sending mail bombs to the US/EU and our solution would be to require all senders, including domestic ones, to prove their identity in order to have their parcels delivered. Completely absurd, but somehow with the Internet everyone jumps to that instead of more reasonable solutions.