In the original, the despairing ending was finding the remains of human civilization, which had destroyed itself.
In the 2001 version, it bizarrely ends with the main character returning to Earth, only to find that he'd changed the past or something and apes ruled in the modern day, complete with a statue of Ape Abe Lincoln.
I suppose the image, with the T-Rex surrounded by puzzled humans, felt more like the latter than the former to me.