Clannad is a really heartfelt anime about a group of friends bonding over various issues, whilst grappling with their past and gradually building their bonds with each other. The main character, Tomoya, feels like a persona protagonist with even more sass, but he is by no means a bad character.
Animation and sound, while simplistic, is very solid and there is very little wrong with it.
The one big complaint i would have with Clannad is that one character, arguably the most compelling of the bunch, gets almost written out of the show entirely, and the writers never give them closure.
Overall. however, Clannad is a great time filled with memorable characters and while it feels like arcs slapped together, it's easy to immerse yourself in said arcs and have a great time.