Well, theoretically you could just use 3-phase motors, right? I'd actually like that, and over here in Germany, most homes have a 3-phase supply in the kitchen for an electric stovetop.
More efficient than single-phase. In this case, it makes the inverter redundant, because the inverter's only purpose is to produce a 3-phase AC supply for the motor.
I think late 90s/early 2000s was the peak of fridge reliability to efficiency ratio.
They run the defrost timer through the thermostat, so defrost cycles are somewhat inline with fridge use.
The circuitry is simple - a defrost timer, PTC "relay", a few thermostats and the compressor.
Newer fridges are a bit quieter and more efficient with inverter technology, but failure rates are way higher due to electronics failures.