I highly doubt a lot of this. First of the dungeons seem shorter because we've only seen the few beginning ones. And since we have only seen a few early dungeons, I don't think we can judge the variety yet.Maybe they made the storyline easier compared to previous PMDs. The dungeons seem shorter, fewer pokes to deal with, less variety in dungeons and you have more dragons on your side.
Speaking of the story so far, I'm glad Kyurem isn't the bad guy. But I wonder who is? And what about the infinite labyrinth? Has that even been mentioned yet?