Character designs are important of course, and it's not wrong to say that characters still look much better in this OVA than they have in animated material that has released since, but a good sense of color and style can do so much.
Art direction as a whole is very important. The Yo Son Goku OVA is a good example of how far it can take you in terms of visual appeal. There are places where Yamamuro's modern sensibilities are still visible in the characters, but they aren't nearly as detrimental or distracting