disagree. IME, the best sounding carts offer the greatest separation.
and 30db, that's if you are lucky. Most carts have separation figures closer to 20db, depending on frequency, including some very expensive models. 25db is more the norm.
Indeed separation is nowhere near CD levels, but I don't notice the big difference in separation between CDs and LPs having an influence on the stereo image, but the big differences between the frequency responses of different cartridges is very obvious in my experience.
Are you sure the bass is raised in mastering? It is very record player and placement dependent but acoustic and mechanical feedback in the bass can be only a few dB down on signal, so no howling but substantial extra bass coming out of the cartridge, the extra bass is very likely to be being created by your TT, not on the LP.
When I first started working in the R&D department at Garrard one of the first thing they did was to get me to do a rumble measurement of a deck. I had been doing noise and vibration research for years by then so I was familiar with the analogue measuring gear from Bruel and Kjaer everybody used. I had the deck on an oak workbench on the 4th floor of the building. I couldn't get a consistent result and thought the deck may be faulty but then one of the experienced guys pointed out it was picking up the traffic driving by on the road below, the other side of the car park! The deck had normal rubber grommet mounts but they do nothing at bass frequencies. Mounting the deck on a seismic mass for the measurement resulted in stable low measurements.
OTOH personally I like the bass one gets from a non-suspended TT even though I know it is an artefact not on the LP.
I have 4 record players, a Goldmund Reference/T3f, an EMT direct drive studio TT and arm, a B&O 8002 (superbly engineered) and a Roksan Xerxes. They all sound different to each other probably because of their different airborne and structure borne feedback signatures adding differing amounts of reverb.