Dear @noromance : " the turntable and its supporting structure has the most significant contribution to retrieval of the maximum amount of data from the grooves. "
Key in your statement: " retrieval of the maximum amount of data from the grooves. " "
look and think for a moment: even if the TT is not exactly precise on spining at 33.33 rpm or any other " condition " the RETRIAVAL amount information fromthe LP grooves ( rigth or wrong ) is the main target/responsability of the cartridge it's why cartridges exist along two other " items " tonearm and our care of that cartridge/tonearm set up.
Yes, with out the spining on TT nothing can happens but that's not the issue in your statement words. After the LP the " source " is the cartridge/transducer.
@terry9 posted that phono stage is first in importance order and makes sense in several ways because it's this electronics unit who has to proccess the cartrisge information but even that the SOURCE still is the cartridge and what surrounded LP/cartridge couple are its slaves, yes important " slaves " as a whole.
R.