Sound quality issues with studio monitors

I have been having issues that it seems there is no solution to on the internet. I have a focusrite interface with studio monitors and an old Yamaha dgx 230 connected to my plenty powerful PC through USB midi. The sound quality for every vst piano is terrible. They sound very thin and brash, with headphones there is a slight improvement, though not much, mainly in volume. Other instruments sound fine though they are more analog sounding through headphones. Why does the grandeur and Alicia's keys and the maverick all sound terrible through my studio monitors? I've tried mono and stereo, I've tried eq, adding effects through the plugins, I tried a very cheap set of speakers plugged directed into my pc with an aux and it sounded basically the same with a little less bass and a little quieter than my krks. I've also messed around with different velocity curves and different settings on the keyboard itself. I find it hard to believe that an acoustically untreated room would make the pianos sound completely awful and quiet compared to every other instrument. I have been wanting to upgrade my keyboard but if it's still going to sound bad, I may have to just go for onboard sounds instead. I have played a 15 or 20 year old keyboard probably midrange in price that sounded tons better than these virtual pianos. I feel like it has to be something on my end and not the quality of the instruments but I can't find any point in the chain that would be a problem.

Has anyone else here had this issue? Do your piano libraries sound at least good? there has been very rare occasions where it seemed like the pianos actually sounded good and I really enjoyed them but 95 percent of the time it's unbearable.