And this meant that car audio systems with a cassette slot were more future proof than car audio systems with only a cd slot.
Aux cable is the pinnacle of car audio sharing technology.
Bluetooth is nice too since you can use the media controls on the steering wheel. In case your mix contains tracks which aren’t fire. Ok I see where I made the mistake. Aux is sufficient.

In case your mix contains tracks which aren’t fire.

Not a problem I’ve ever had.

Didn’t see those myself until they already had USB
Until the to the fucking jacks out of the phones