Jurassic Park resolved a lot of 'popular' myths about Dinosaurs (slow, stupid, upright) but introduced in time myths of its own (8-feet tall Velociraptors, frilled Dilophosaurus). Every time I mention Dilophosaurus in a conversation (and that's 0.3% of my yearly conversations) I have to point out that no,
we have zero proof that Dilophosaurus had frills, because a good lot of people are convinced that
they absolutely did, based on what they saw in
Jurassic Park.
Spielberg wanted lifelike animals, and wanted them to feel real and up to date, but that did not stop him from making certain artistic choices when he felt like it. And so he did in the second movie. And so did Johnston in the third. In the same way that we can accept that frilled-Dilophosaurus is just 'speculative', we can also say that the scaly Raptors are due to 'speculative' reasons; who's to say that the feathers were not a characteristic of a certain age span -- and that later in life they shed them and develop scales instead? What if they are an undiscovered species that regressed to a scaly configuration? We can play with that however we want. Point is, we'll never know.
You also have to keep in mind that the
Jurassic Park Tyrannosaurus and Velociraptor are some of the most well known movie characters, and their look has become embedded in the public imaginary -- changing the Raptors so radically, in a
sequel no less, would influence the film negatively. The filmmakers know that. Were this a remake, or something separate, it would be different. I'll absolutely welcome another Dinosaur movie with up to date Dromeosaurids.
I'm an enormous enthusiast of all things Dinosaurs, and would love to see up to date creatures myself -- but I absolutely understand why they would keep the design very much parallel to its precedent incarnations.
Vertigo forgive me.