Aside from the practical and technical problems you're greatly limiting your audience. Most people who don't travel internationally don't have a passport. In Europe this might be a smaller number but in the USA and Canada I would guess this is a majority of people. Non-citizens won't have a passport. Most young adults will not have one. Many older people will have let theirs expire.

What about people who buy stolen passports on the dark web? Or passport details that get leaked in data breaches

How do I know that, you will handle my passport data with care? Banks I can trust(despite numerous leaks), you as a random social media or online service with zero regulation, I won’t. Plus this opens up immense ways to sue you for collecting unnecessary data and personal information, unless you are massive and have an army or lawyer or have a KYC requirement.

Why would I ever give my passport to your website or anyone elses?

who is going to upload their passport to use social media?

No passport, but perhaps face picture that is also encoded with on device verifiable token.

I think there is actually a use case for blockchain (don't pile on!) for this. I have a vague idea of a unique token that goes on every camera and can be verified from the blockchain. If a picture has the token you know it's real... like i said, it's vague idea but i think it's coming

Why not require a non-voip phone number instead of passport?