True. archive.org complies with removal requests from site owners [1]. The problem is that the content most worth preserving is exactly the content people try hardest to get taken down. If archive.is goes down, and between the FBI subpoena and the Wikipedia ban the pressure is real, archive.org becomes the de facto monopoly in web archival. A monopoly that honors takedown requests is not a reliable record of history.
also, archive.org only verifies the current owner of the domain for takedowns. So if a site was hosting content, that content was archived the site then shut down and someone else acquired the domain, the new owner could request the removal of the old content.
[1]: https://help.archive.org/help/how-do-i-request-to-remove-som...