As long as your turntable has the following figures:
rumble < 75 - 78 db,
wow & flutter as low as possible,
speed stability better than about 1%
and as long as your tonearm effective mass is a good match for your cartridge,
here are the approximate importance of the components:
turntable: 10%
tonearm: 10%
cartridge: 40%
phono amp: 40%
This ∆∆∆
It is easier to choose and to know what you have if you have numbers on the performance.
Otherwise it is just bla bla bla Words that confuse..
One thing that you can look at is if all types of adjustments parameters are available on the tonearm incorporated on the TT.
When cartridge is ~40% and you can't adjust for example SRA then you leave some performance on the table.. .. especially when you have advanced stylus shapes. (even better is if the TT has SRA on the fly adjustment). Now you can easily argument that a TT should sound better than one that cannot adjust it all.