In a way the Bible does mention dinosaurs, or if not dinosaurs, then large reptiles. This is the only animal in entire creation account with a size attributed to it. Taninim is occasionally translated as whale, crocodile, lizard, even dragon. The confusion over the meaning of taninim is surprising since it is a word known elsewhere in the Bible to mean reptiles. Dinosaurs were certainly the big reptiles.
Many people discard the Bible's teaching because it seems scientifically incorrect.
Clerics with the scantiest scientific knowledge were, and still are, willing to trash every scientific discovery that seems to encroach upon their imagined sacred turf. First Copernicus in the 1500's had the audacity to suggest that the Earth moved around the Sun. This was unacceptable to the religious establishment not withstanding that the opening sentence of the Bible places the heavens before the Earth. Copernicus was a believing Catholic. The discovery didn't shake his faith.