keys.openpgp.org is the semi-canonical key server for OpenPGP. Certainly there are other key servers, but it makes more sense for us to look up keys on a keyserver hosted under openpgp.org than one hosted by Ubuntu or any other single entity. KOO is a community-led and -governed project. It now even has elections and a board (which we joined): https://keys.openpgp.org/about/news#2023-04-28-governance
WKD is great, but can't be used by people with email addresses under domains that don't support it. So KOO fills that gap.
Yes, KOO is a good intermediary, but it still matters: there are no agreed-upon mechanism saying it should be used in all cases. You took this liberty. Why not even ask the receivers, aka those who know, if they're ok using that key ?
We can't easily ask them that. KOO could ask, though, since that's what the user's interacting with when they're uploading the key. And, I do agree that the signalling could be improved, there, so I'll discuss it with them.
WKD is great, but can't be used by people with email addresses under domains that don't support it. So KOO fills that gap.