This has also been my experience over the years. My suped-up 4-core beats my 12-core; both with tons of RAM and SSD drives.
Also my experience, as well.
Interestingly I found Cubase’s inefficient multiprocessing has bizarre ceilings. For example, I can load about 50 instrument tracks, each with one Kontakt instance and ASIO load steadily increases to 20-50% steady load. But once you reach a certain threshold, say 55 instances (it varies depending on the machine and other factors, but generally you can predict around what track count), the ASIO meter will go insane and max out and the whole session grinds to a halt. This behavior is exhibited in the best of circumstances (the right ASIO Guard settings, buffer settings, etc) and only goes downhill if any of those settings are less than ideal.
In contrast, I can load (and play) 200 Kontakts inside of Logic Pro X without much problem. Also, VE Pro can take dozens if not hundreds of Kontakt instances.
So yes, there is something amiss with Cubase’s internals. I just find workarounds - disabling instrument tracks I don’t need, offloading some things to VE Pro, etc. Frustrating but I’ve lost hope that the situation will improve without a total rewrite of Cubase.