To get back to the question...
1. Some of us who have tried (even if that just means swapping from sideboard/ book case to Naim Fraim/ Quadraspire/ Isoblue racks) reckon that what is under solid state kit can make a small difference to SQ. Some even think that in some rooms and systems, modest additional improvement is possible.
2. Plenty of other people either assert that there can be no difference, or that they have really tried and heard nothing but their own expectation bias.
3. Almost everyone thinks that what goes under a turntable is important for SQ, even if domestic realities mean some compromises.
4. The jury is still out on what goes under speakers, but...
If i have counted correctly, 40 PFMers reported on Isoacoustics Gaias back in 2020. 7 thought they made things worse and 32 thought they gave an improvement. 23 mentioned or showed their floors - at the margin, the naysayers are slightly more likely to have carpet rather than sprung floorboards but the difference is not clear and the sample size very small, and much the same applies to standmounts versus floorstanders for what benefits more/ less.
The most consistent comment, even more than 'tightens up the bass' was probably the advice to get a set on 30-day trial and listen in your own home. I suspect strongly that that isn't a bad summary for what most of us are saying here.
Does any of that look wrong?