Many people hate clannad because it's "slow" at progressing in the story but that was what made the ending so emotional. The first season ties you up with the characters and the second season shows the problems they face causing you to get the feels.
Many people don't like this couple (main couple) because it is based on a game (visual novel) and there are other great characters you can choose to be with the main guy.
There are a lot of romantic routes the story could have turned to. Since a lot of people didn't favor the main girl so much, the creator are creating more animes of the other girls with the main guy. If you can't wait, just go support them by playing the game.