Is the goal of isolation under the feet only for foot steps and effects of bass?
No. As Johnnyb53 explained just above:
The stock footers on the Technics are not very good. In spite of their serious look, they don't isolate well from room vibration nor do they drain internal vibrations from the turntable.
Both goals are important, though different.
Isolation from structure-borne vibrations prevents mistracking/skipping and lowers the system sound floor. As such vibrations tend to be at fairly low frequencies, reducing them reduces the LF mud that gets into the system, which reduces the work for every component in the signal path. The sonic result is blacker backgrounds and the ability to hear lower levels of detail.
Draining vibrations that are already in the rig (motor vibrations and stray energies escaping from the cartridge) has a similar effect, but as such noises can occur at many frequencies, their effects, if not drained away, are more complex. But they're always noise, so less is better.
Improving bass and dynamic response requires that the turntable be as immobile as possible. The turntables which produce the lowest, tightest, strongest bass and punchiest dynamics are high mass designs. Suspended and lightweight tables allow the tail to wag the dog, so to speak. To whatever extent this occurs, dynamics and bass response will suffer. My TT weighs nearly 90 lbs. It has better dynamics and bass than any light/suspended table. But even this fairly heavy table suffers weakened bass and dynamics if I put overly compliant footers beneath it.
From the above, you could correctly deduce that isolating from external vibrations while maintaining maximum bass and dynamics are somewhat conflicting goals. This makes finding an optimal support solution for any particular turntable/tonearm/cartridge a matter of experimentation and sometimes luck.
