>>10825159We can never know exactly how they looked, but there's a lot more fossil information about their appearance than lay people realize or that scientists in the past realized. Lots of dinosaurs are actually fossil mummies or have had at least part of them mummified. We know that concovenator had almost snake-like belly scales because of how well it was preserved, we know the scale patterning of Edmontosaurus thanks to a full mummy and what color the feathers of sinosauropteryx (red with white bands like a red panda), Archeopteryx (black), microraptor (iridescent black), and several other feathered dinosaurs were because certain pigments leave distinct isotopic signatures as they decay. We know that even though Yutyrannus was covered in feathers (two of them died in a volcanic lake in China and were almost perfectly preserved) later Tyrannosaurs lost their feathers almost completely because there's actually an extensive number of Tyrannosaurus scale fossils.
And for the hippo issue with "shrink wrapping," that's become significantly less of a problem as scientists have come to better reconstruct the size of muscles based on the scaring left on their bones and the weight estimates their bones could have supported. That's why Tyrannosaurus Rex has gone from being depicted as weighing 8 tones to between 10 and 12 tons.
You're right, it is impossible have a 100% accurate reconstruction, but it is possible to have a reconstruction accurate to what we know about the animal now which shouldn't change too much in the case of most animals (Spinosaurus and a few other unfortunate animals that had most of their best remains destroyed during WWII notwithstanding). The JP reconstructions, outside of Triceratops' feet and the raptors being too large were pretty scientifically accurate to the late 80s and early 90s, but that was 40 years ago and a lot information has given paleontologists better information to build a better picture of how they would have looked.
