I found it to be the opposite. The characterization of Sora and Riku was probably the best of the series, and their interactions were very natural and refreshing. The story was a bit of a retread of KH1, but it didn't try to repeat the stories of those world's and instead did something different by having a few twists on roles and turnouts (and was better executed than CoM and I love CoM).
The gameplay was one big homage to video games and each style did something fun and unique. The mechanics introduced also remain to be the best improvements in the series (Keyblade upgrading revitalized their worth by having different skills/finishers you could select, the skill tree felt rewarding). The plot points introduced in the game reinforced the concept that all things can grow hearts. The game is held back by the limitations of the DS, though, and the fact it is a retread.
It is fine to not like the game but you should understand that some people do find it fun.