Even "effectively re-centralized federated" will still provide much better ways to keep all that browser fingerprinting stuff and the like away from Meta et al than a closed system. E.g. if for some reason you need to operate a Google email address you could run the day to day read and write behind a forwarding setup never connecting your regular browser or your imap client to Google servers, dealing with the occasional setup/maintenance from a browser properly isolated from your search history and the like.
