With regards to video hosting websites maintaining identification information, it's possible to provide this functionality without they themselves storing sensitive user identification data. Third party providers (ID.me comes to mind) could be utilized to do so, with adult content hosting providers treating this data similar to payment data and the PCI requirements that go along with it (store the verification/attestation token and timestamps, not the data itself). I would agree that I wouldn't want Pornhub storing my passport photo and metadata.
Finally, to your point about preemptive vs reactive, in the case of adult content platforms, it seems reasonable to require preemptive documentation considering the record keeping requirements for producing adult content. Refer to 18 U.S. Code § 2257 for specifics [1] [2].
[1] https://www.law.cornell.edu/uscode/text/18/2257
[2] https://www.eff.org/issues/bloggers/legal/adult (Control-F "Who is required to keep records about adult images under federal law?")
>Why should someone be able to upload whatever they want to platforms with no responsibility for what they’re uploading?
This isn't in question though. The question is whether sites need to be preemptive or reactive. Illegal content is illegal even right now and these websites will delete it. If they don't then you can take them to court and the content will get deleted. However, the thread suggests that these websites should be forced to be preemptive - to demand documentation upfront. That's a whole different situation.