Proper setup trumps all, and has the most potential.
you said in your opening post.
most turntables, especially decent ones, have vibration control measures built into them via footers and various construction techniques.
This shows to me, that you understand that manufacturers consider vibration control important.
but then you say in your next post.
I have not bothered to perfectly level the rack’s feet so there is some play / wobble if disturbed.
Well, one can wonder if this is due to laziness ? Who knows, but it is wrong for basic 101 turntable set up, and no one questioned it. The TT platform/stand, whatever type/s - plural - as some use multiple products, under the TT, is/are but an extension of the turntable. Adding an isolation platform/s *whatever cost' under it may get better results, but it is a band aid, if the basics are not in order to begin with.