okay so clearly you don't know what you're talking about because they do use existing standards/DNS as the primary way to validate domain ownership. It's free to not say anything and read the comments first before going off about something!
I'm not going to speak for the commenter you're replying to, but I don't think anyone here is talking about the standards-compliant, DNS-based domain verification system. I think we're all talking about the non-standards-compliant, /xrpc/-path verification.