[William Sommerwerck]

It is possible to make very good recordings on Compact Cassette, especially
with metal-particle tape on well-engineered three-head decks. (I know,
because I've done it.)

The real problem with cassettes is that they're not archival. Not only is
the tape itself mechanically fragile, but the wavelengths are so short that
the recording gradually self-erases at high frequencies, even with Type IV
materials. (Again, I can verify this from experience.)