The time to restore from backups after a ransomware attack is more about figuring out how they got in and closing any back doors then cleaning out the existing systems, applying the latest security updates etc., rather than actually restoring the backups from tape or whatever.

The last thing you want is for your backup to restore whatever back door they installed a few weeks before they launched the actual attack, or to leave the unpatched system (or whatever it was) open and immediately have the attackers encrypt all your files again.

High end tape reads sequentially faster than a typical spinning HDD, so it should be possible to design for rapid full restores. Rapid restores of specific files (e.g. to recover from accidental deletion) would be slow from tape though, so are probably best served by online snapshots rather than the DR backup.