Tape is also incredibly slow and difficult to scale. Also, the equipment needed to operate a cluster of tape archivers costs a lot, while they are using their own designs dor servers, with coXmmodity hardware in them.
Tape is slow only when you need frequently to read some random part of it, because you might need a couple of minutes to go till the other end of the tape.
The reading/writing speed of tapes is excellent, better than that of hard drives, so writing a backup takes less time.
For archives that are accessed only infrequently, tape is more reliable and also faster.
If you want to have access in less than a minute to any part of your backups, then yes, tape is inappropriate and you must use HDDs.
And to backup a NAS, it requires to regularly change the tapes. Any backup that requires manual steps is likely to be delayed and to be too infrequent to be useful.
