Michael Fremer has written, and I agree:
"Regulating a direct-drive motor's speed with a phase-locked loop produces tight speed control and measurably low levels of wow and flutter, but the motor's constant, ultra-high-speed hunting and pecking as it over- and undercompensates in the attempt to produce a consistent speed can create a jitter effect in the mid-treble to which the human ear is particularly sensitive, adding a hard, brittle texture to music. That describes the sound of Technics' now-discontinued SL1200 series of direct-drive turntables, and explains why, despite their high build quality and relatively low price, few are used in serious audio systems, though some listeners claim that these 'tables can be modified to improve their sonic performance."
That doesn't mean that DD cannot be built that doesn't have this issue. It has been done for generations, but they have usually been quite expensive. As the prices of high performing belt drive TTs has gone up and that of high performing DD TTs has come down (as for ex. VPI) the market is changing.
"Regulating a direct-drive motor's speed with a phase-locked loop produces tight speed control and measurably low levels of wow and flutter, but the motor's constant, ultra-high-speed hunting and pecking as it over- and undercompensates in the attempt to produce a consistent speed can create a jitter effect in the mid-treble to which the human ear is particularly sensitive, adding a hard, brittle texture to music. That describes the sound of Technics' now-discontinued SL1200 series of direct-drive turntables, and explains why, despite their high build quality and relatively low price, few are used in serious audio systems, though some listeners claim that these 'tables can be modified to improve their sonic performance."
That doesn't mean that DD cannot be built that doesn't have this issue. It has been done for generations, but they have usually been quite expensive. As the prices of high performing belt drive TTs has gone up and that of high performing DD TTs has come down (as for ex. VPI) the market is changing.