What bugs me most is that they failed to make Bron's story in any way plausible and from what he says and does throughout LBT I can't help thinking of him as a very irresponsible, careless, and even coldhearted character.
I don't believe Bron was a cold-hearted character, or irresponsible. He is a very loving, caring, and devoted character. His story was just fine. He left to find a better home for him and his mate, and unborn baby. To leave to do this was a noble act, and I admire him for that. It's not his fault that, when he returned, the land changed and he couldn't find Littlefoot or his mate.
He had no idea where Littlefoot was, his name, what he looked like, no one could give him the information he needed. He didn't even know if Littlefoot was still alive or not. What could he have done?
He chose to stay at that valley rather than look for the Great Valley most likely because he had lost all hope. After all, what if Littlefoot had been killed? The barren land was large and vast; anything could have happened. I would think that poor Bron was at his wits end, devastated that he couldn't save his mate, that he wasn't there to protect her. As much as it probably pained him to do this; he had to move on, and start life anew.
I apologize if I offended or upset anyone.