There are other types of motors that rely neither on magnetic fields nor electrostatic fields, for example the ultrasonic motor which is commonly used as a focusing actuator in high end camera lenses. They use the piezoelectric effect to cause a semiconductor material to physically deflect and "push" the rotating part around in circles... or in a line in the case of a linear USM.
Those are pretty neat. Their main advantage is being able to move quickly and with extreme precision (think down to nanometers). They're not particularly strong or efficient.
I'm sure this has already been invented, but I don't know the proper terminology:
Two or more motors with different characteristics that are somehow geared together, so that the X% errors in speed/position of a more-powerful motor get fixed by simultaneous activation of a finer motor (possibly in "reverse") and so on down the chain.
I suppose it hits diminishing returns whenever the main source of error comes from all the connections or gears.
I wager the electric motors actually have a very low angular velocity error on average. However given the way they work, during a revolution you likely have non linear rotation of the shaft on a basic motor due to the classical physics of the rotational load accelerating between its push/pull magnetic poles. Theres some interesting work in the motor driver space trying to smooth out the curves in the motion profiles of the trusty stepper motor (see TMC2209 driver promo content) and surely similar work for other electric motors. I bet one of our peers here could speak more authoritatively than my conjecture above.
https://www.piezo-motor.net/
https://www.meddeviceonline.com/doc/what-are-canon-s-linear-...