yea... what is a decentralized way of proving humanity?

One way would be, that we prove each other when we meet in real life. Maybe even locking coins, to put value behind once declaration. If it comes out as a hoax, the coins are gone? I see no way around proving each others identity in real life. When AI or some algorithms are doing it, it maybe can not be easily cheated at first, but once it can, it can be automated and then its game over. Better relying on humans proving humans. Maybe not perfect, but what will ever be? Worldcoin i.e. could be hacked and millions of new identities could be generated by a mouseclick.

I think a smart contract that relies on a government document could work https://home.treechat.ai/quest/227d6b24-0c8f-4025-bda2-eab619706017