Any analog recording medium is 100% at the mercy of how much care went into the mechanics.
The tape head is essentially a stethoscope in direct physical contact whith every other part in the machine, and even the table it's sitting on and your house and the world.
Every part of it from the quality of the bearings or bushings, or lack of either just plastic parts rubbing directly on metal pins, the motor, gears, all of it is present in the physical motion of the tape, which is directly added to the signal you get out of the head.
It's like putting your ear on any machine, you can hear every single part inside the machine.
It can't be fixed by electronics In the same way that you can't unscramble an egg.
You can only fake improving it with filters that really just modify the signal even more. It may sound a "better" if one of the worst components is a big simple crude regular motor pulse or ac hum, and a filter can somewhat match that well enough to make it less noticeable, but the resulting output is even further deviated from the original signal.
Digital does not have this problem because a bit is a bit. A bit that barely registered and a bit that came from a strong signal are both the same bit once read, and even some amount of incorrect bits are repaired by math and redundant data.
And digital doesn't care how slow or fast the bits come. Any deviations from imaginary perfect media speed aren't turned into audio signal because the data is not being turned from physical aspects of the media directly into sound like a stethoscope, it's just a block of data that could arrive at any speed, and the audio is fabricated later by interpreting the data. The audio there is determined by the quality of the dac.