I was skeptical for decades about the sonic benefits of a rack, but finally had one built because I was tired of having gear sitting on the floor.
Had a friend who's an artisan build it to my specs.
1.5" butcher block hardwood.
1" square steel tubing.
All tubing filled with sand.
Shelves isolated from tubes with silicone.
Tubes isolated from wood floor with hard rubber discs.
I was only wanting things to look better, but to my surprise the sound quality also was improved.
So yes, in my case a well-designed rack did make a difference.