Cloudflare is discriminatory. They, and their fanbois, will likely claim that they can't publicly discuss their criteria for who they block, so some mysterious magic is going on in the background, and we're supposed to just trust them because they're big.
That in mind, I'd love even the most fawning of the fanbois to come up with rationalization for why for a very common browser (Safari on modern macOS), most links through Cloudflare work, but trying to get past the are-you-human checkbox on Cloudflare's abuse reporting page doesn't work half the time.
Obviously that shouldn't be on an abuse reporting page at all, but Cloudflare has been making abuse reporting extremely difficult for years. Adding rate limiting (a human can easily hit it) and prove-you're-human verification on their abuse page just unambiguously proves this.