Cloudflare's protection is to guard against traffic spikes and automated malicious attacks; Google and social sites are allow-listed because they're trustable entities with well-defined online presences and a vested interest (generally) in not breaking sites. "How do we do away with the need to put up an anti-automated-traffic screen plus whitelist" is in the same category of problem as "How do we change the modern web to address automated malicious attacks?"