Isolation stands: snakeoil?

"Soft materials?" You mean sorbothane? Why the circumlocution?
I worked with airborne sonars at one time and am sceptical about the transfer of acoustic energy to turntables through the air, since depending on frequencies and the size of the turntable or its components, the sound may bounce back or pass right by. Also the impedance mismatch between air and solid objects is considerable, so I can't see much energy getting in that way.
In any case why are there no measurements of this phenomenon to clarify what is going on?

The best turntable islolaters are the doors between the speaker room and the electronics room.  My ex-laundry room has all but the speakers. Of course, guests are not as impressed with the array of electronics, but that was never my goal. Another big benefit of this is the dryer's 10 guage wiring that now comes from a 30 amp 110 volt dedicated breaker.

I have my TT suspended through the ceiling by four cables into eye hook lag bolts threaded through a 1/2 inch glass shelf with nuts on the underside for leveling. Eliminates all vibration except for what travels through the atmosphere of the listening room. Cables are secured in the attic to conduit pipe that spans the roof trusses and is held in place with conduit brackets. I can't think of a better way to isolate a TT other than having it in another room far from the listening room.

I am moving my equipment, including a turntable, to a room other than where I have my speakers.  I have a wooden floor, with a crawl-space below. I have to drill holes thru the floor to run speaker cables underneath. I was thinking of drilling 4 more holes, each for one leg of my stand, and running rebar, or similar material right down into the ground, and suspending my stand on those steel rods with no floor contact. Thus, for vibration purposes, I am truly grounded, and the washer and dryer on other side of the wall will not affect my system. Thoughts?

What’s shakin’? Uh, the whole house is shaking! Not just the listening room. You know, due to all the traffic, Earth crust motion, wind, ocean waves hitting the shore, what have you. Besides it’s a no brainer to isolate the speakers these days, it’s really quite the fad. Saves a lot of time and effort.