I totally agree, man! The way the T. rex is first introduced into the plot of TLW is actually my favourite intro in the franchise; with the loud, distant, distinctly angry roar in the distance, followed by the impact tremors, frightened birds and rustling trees beneath the high hide was the perfect build up to the T. rex reveal. It felt like if I had gone back in time to Late Cretaceous Montana.
Even though I accept that Rexy was an old dino by the time JW came out, I do wish she had given a stronger, mightier roar upon reclaiming the island. As for the sequel, I hope that the film introduces a young male Rex that's as vicious as the T. rex parents in TLW. I think Rexy is the only T. rex that should really be allowed to be a "hero", since she has been built up over the years as this larger than life presence with saving the humans in the visitor's center and battling the Indominus, and that's the limit.