How do stands remove airborne transmission of sound from speakers to the turntable?
While I don't disagree in general us audiophiles tend to go over the top on such topics. Others ... don't.

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Needless to say that my equipment sits on two separate racks, 50 kg each, equipped with
Super Spikes and separately decoupled shelves. Not talking about the Clarity Stands with their 22 kg base plates. Looks like I'm an audiophile ...
It's more than appropriate in many cases. I wouldn't use it in MC mode, sure. But in my experience it's perfectly fine in such an environment.
Sure... get the cheapest possible used turntable from Goodwill, use a pair of PA speakers, make sure your 5 dollar Ronco cartridge is playing with a tracking force of 4gm on that plastic tonearm... Get a sound meter and do not do ANY listening at all and then pass judgement on YuTube.
It's not being an audiophile... it's just plain listening to the music. Heck, everyone that is posting here have at least a reasonable entry level turntable and speakers
Imagine if you will, having an entry level Rega with no suspension. They are good sounding turntables, not High End but not bad for an entry... put them on the same shelf with reasonable good sounding speakers and see what happens. OK, now, either move the speakers out away or put some isolation between the speakers and the shelf and try the same experiment.
My Target stand is filled with lead shot and it has levelled and spiked shelves. It has spiked feet into the hard footers than sit directly on the wood floor which sit on the slab. The turntable has the Trampolin 2 and Keel subframe... so you got a set up that "sinks" vibration away from the record.
The issue in having the speakers and turntable directly on the shelf is the direct transmission of the low end vibrations which carry the most energy.
And, as you point out with your own racks, you can actually hear it. Those speaker footers I recommended do some very good things... for one thing, they allow you to tilt the speakers so they point directly to your ears, for another they really isolate the vibration. Lastly, they are nice looking. I mean, you can get them from Amazon, give them a try and if you don't like them, return them. For my wife's case, she doesn't have a turntable but the speakers sat by her wide monitor. Getting the stands allowed us to tilt them nicely and she doesn't "Feel" the music on her keyboard.
Bottom line... IMHO, decoupling the speakers from the turntable will yield and improvement in the sound... it will make the bass better sounding.. tighter, cleaner.
Phono preamp... for a couple of hundred dollars or so you can likely get a better sounding MM phono stage. Use the line in inputs of the Ultra. I don't understand why WiiM put that in there.