The WebPKI and DNSSEC run global PKIs because they routinely introduce untrusting strangers to each other. That's precisely not the SSH problem. Anything you do to bring up a new physical (or virtual) involves installing trust anchors on it; if you're in that position already, it actually harms security to have it trust a global public PKI.
The arguments for things like SSHFP and SSH-via-DNSSEC are really telling. It's like arguing that code signing certificates should be in the DNS PKI.
Providing global PKI and enabling end-to-end authentication by default for all clients and protocols certainly would make the internet a safer place.
Do you hardcode Github and AWS keys in your SSH config? Do you think it would be beneficial to global security if that happened automatically?
Further, I haven't "moved on to another argument". Can you answer the question I just asked? If I have an existing internal PKI for my fleet, what security value is a trust relationship with DNSSEC adding? Please try to be specific, because I'm having trouble coming up with any value at all.