All the other dinosaur species could talk, except the Velociraptors and the Carnotaurus. Why couldn't they speak?
They couldn't talk for the same reason they were much larger and scarier-looking in the movie than real-life carnotaurs--for drama.
"Eric Leighton, one of the directors, basically admitted . . . that they would "cheat like hell" because they were not creating a documentary." (Tvtropes- https://tvtropes.org/pmwiki/pmwiki.php/Disney/DinoSAUR)
Not allowing predators to speak in talking animal stories is common. In The Land Before Time movies, plant-eaters speak but the sharp-tooth can only roar unless in a sequel a cute baby one shows up.