I'm always mystified why we haven't leveraged DNS.
I mean: why not have cookie policy set by a flag in DNS? Not unlike DKIM or even SSHFP.
Of course, we wouldn't need the entire certificate industry if we simply looked up a site's PK along with its DNS record...
No, we wouldn't, you're right. We'd just replace LetsEncrypt and the ISRG with the security track records and policy integrity of the major DNS providers, many of which are state-controlled, and the largest of which are too important to revoke.
Really hard to understand why that hasn't happened yet!
You're talking about DAME (which email uses). It has it's own issues like not having transparency logs, and if a DNSSEC signing keyholder goes rogue, there is no easy way to revoke trust (unlike CRLs for Web PKI).