As someone who has been around since C2 of the old version, I'm actually starting to enjoy the new art more than the old one. The old art felt more airbrushed and flat, whereas the new one feels far more gritty and 'real', if you can even say that about any type of art that isn't drawn to be specifically 1:1 to real world stuff. Like the old art wasn't bad, but they didn't look as much like humans as they do now. Like the MC has freckles now, whereas her old sprite just felt too smooth to look human. All of the characters honestly look more alive now, when the old style just made them seem artificial. I don't know if my description makes sense to anyone else though.
Edit: As an example. The old art made everyone look like they were standing in front of a studio light at all times, but now they have proper shading which in and of itself adds a lot of dimension to their faces.