I think one of the problems could be that they used really high-polygon models by 3DS standards.
Other games, like RE:R look better because of the style and effects used, but the models are not as detailed.
Of course, I have no knowledge of how the 3DS' GPU handles the rendering so it's just speculation on my part, but a look at the Pokemon models is enough to see how detailed they are, even though the textures are not great on some mons.
The other part of the problem could be that GF didn't have time to optimize the game, which (please correct me if I'm wrong, anybody who knows about 3DS games) could be fixed with a patch, albeit a very big one.
Other games, like RE:R look better because of the style and effects used, but the models are not as detailed.
Of course, I have no knowledge of how the 3DS' GPU handles the rendering so it's just speculation on my part, but a look at the Pokemon models is enough to see how detailed they are, even though the textures are not great on some mons.
The other part of the problem could be that GF didn't have time to optimize the game, which (please correct me if I'm wrong, anybody who knows about 3DS games) could be fixed with a patch, albeit a very big one.