As others have mentioned, the spring and mass system has to be properly designed for it to effectively isolate. I still have an old VPI HW19 (original, not a later Mk X or Jr. version) in a closet, that I never bothered to hook up. It uses springs, but the arrangement just seems all wrong - there’s just no way it’s going to be effective. Thank god I eventually purchased a SOTA Star III, and got into vinyl right. The SOTA’s spring suspension is properly designed, and extremely effective at isolating. You'll be hard pressed to find anything more effective without getting into fancy rack systems.
Turntable isolation
My last turntable was a VPI HW19 MK4 .... with the springs. It's isolation from footfalls was terrible on wood framed floor. Are the modern tables with sorbothane feet better at isolating?