this is almost humorous, you folks are arguing about problems the older among us had to deal with in Dual and Phillips TT's of the 70's and 80's.
If speed of a TT is constantly off the musical pitches will be off. Since all speeds are off proportionately, harmonic structure will still be intact. If its badly off the spoken/sung word will sound distorted because we are sensitive to the cadence of speech. Trying to play an instrument along with this becomes silly because you have to mistune your instrument.
If the speed is variably off that becomes wow/flutter... thats musically unacceptable.
What makes the finest turn tables is damping/filtering vibration at the micro level to prevent vibration reaching the arm and platter that would superimpose on the stylus tracked vibration, distorting the electrical signal created in the cartridge and played back as sound in your system. As an example put a vibrator on your cheek and try to sing... thats what a badly isolated TT does even with perfect speed.
You can consider direct drive the equivalent of attaching a vibrator directly to the platter... Denon tried to sell a lot of these.
Next best is belt drive... the motor still vibrates but the belt provides isolation in power transfer. But a platter mounted on same sub chassis as motor still sees vibration transfer through the chassis. Rega follows this model.
Optimal is belt drive, suspension TT where platter and arm are on an independent subchassis... both are isolated.
Linn Sondek,the AR and Sota follow this model
And there are the exotic designs ( I believe I once saw something that floated the platter suspension in the equivalent of jello)