Love it or hate it, here’s one thing Clannad undeniably excels at: character animation. If you observe the visuals closely, much of the characterisation is expressed through body language and subtle visual cues. Even when the anime goes for low-brow, physical humour, the characters’ entire bodies remain quite expressive and dynamic. This is in contrast to the rather “stiff” delivery in most anime comedies.
If you don’t believe me, just observe Nagisa’s drunken scene and Chitoge’s one in Nisekoi. It boils down to the same joke, but there’s a world of difference in the delivery. It’s not so much that Clannad is more skillfully animated (although this is definitely true), but rather the storyboards themselves were conceived with quite different intents in mind; each shot in Clannad draws attention to the movements of all the characters inside and outside the frame, leading to a natural escalation of the situation, whereas Nisekoi’s scene is full of choppy transitions from one key frame into another.
Clannad’s visual strengths were particularly noticeable in the After Story portion of the tale, especially as far as Ushio’s characterisation was concerned. It would have been so easy for her character to become Generic Moeblob #85934, especially given that her role in the overall narrative is mostly one of symbolic importance. Yet Ushio never failed to have presence whenever she was onscreen, and much of this comes down to the way her body movements were animated. It was clear that the key animators put extra care into making her move like a real child.