Dragons
The monster manual does not include any good dragons.
Now that you have let that sink in, I will discuss. They have always been part of the game. The trend of destroying a connection to the themes of the past editions continues. As I see more of this disregard, or intentional destruction, I am less likely to give the game rules a chance. I will still review them and do a fair analysis, but as more basic thematic concepts change, I can't see using them useless they are spectacular and leaps ahead of 3rd edition rules.