I hate to be the one to rain on anyone's parade, but the art isn't just a manner of taste - there are actual anatomical mistakes very clearly evident in how both the sprites and the CGs are done, the line-art is shaky and there is a stiffness about the characters which looks odd. Not to say that the art is bad in a general sense, but yeah, compared to a lot of other dating sims it is not really held up to that standard, considering it's a paid service.
Now, I draw a lot myself so it might just be that I am more sensitive to this than others, but I showed the game to a couple other of my artists friends and the general consensus is that it's not... outstanding.
I've played "Coming Out On Top" and that game is in a very different league art-wise, so I feel like there is no reason to pull that game out to make a point of people preferring that style. Both styles are semi-realistic. Preferences are a huge thing when it comes to art, but there are also certain aspects of it that are simply either done correctly or a mistake - it's the same as enjoying someone's singing voice and still being able to pick out the false notes.
Honestly, I would say the style of "Heirs and Graces" kind of reminds me of ''The Royal Trap'' only less successfully executed.
Alas, there is always an aspect of taste involved, and I did enjoy the game as an overall experience I just feel like everyone keeps fronting that the art is objectively good while if you did actually take it to an art-teacher there would be a certain amount of redlining required.