I'm not saying it's bad. I like his art, it's just often not that consistent. He can create really great panels, it's just that the characters aren't really drawn consistently.
Looking at other mangaka like Shun Saeki, Yuuki Tabata or Horikoshi, they all draw their characters pretty consistently well.
In Furudate's case they just look off a lot of times. I feel that for example Posuka Demizu and Yuusei Matsui have similar issues with their art. Again, I don't dislike the art, I actually like it. It's just that the art still has room to improve.
The Haikyuu anime is a good example for that, because it draws out the true potential from Furudate's character designs. Basically if the art from the anime were to be translated into manga, this would be the kind of consistency that Shun Saeki, Tabata or Horikoshi have.