Isn’t it ridiculous that a long-established site worth billions of dollars takes of the order of a day to provide a gigabyte or so of user data, requiring several continuations separated by several hours (because of outdated data limits), when this is needed?

Time to upgrade the service: allow download of all activities for a user in one go, efficiently, with some reasonable limits on how frequently it is done if that is deemed necessary (to avoid excess use without benefit). The weird thing is, even a limit to one complete download a day would not actually be more restrictive than what already exists in terms of bandwidth - it would just mean that users get done in minutes what currently takes days.