Dynamics and tone are certainly important characteristics of a reproductive system but timing is solely up to the musicians.
That may be correct in terms of the music, but not necessarily playback. The reality is that if you have phase or frequency response aberrations in a system, it can easily alter your perception of timing when listening, or at least mask the "intent" of the musician.
Example - the other night I was sorting out some records and found Jazz at the Pawnshop on Propius - hadn't played it for many years so I put it on. The changes in tempo of the individual instruments for example are easily heard along with the interactions between the players - in a system with phase or frequency errors these attributes can be ameliorated or even lost.
Turntables are a lot more than just a time machine - they provide a foundation for the arm & cartridge to accurately track the groove. It is a base for a mechanical measurement system. Why do you think sensitive measuring instruments in laboratories are often placed on isolated antivibration platforms.
If you cant hear differences between turntables with the same arm/cartridge then just get youself a Technics 1200/Shure V15 and you are good to go. But that does't mean other people cant hear differences.
