Obviously the builds people do of those prototypes are wicked. But everything from Rebels is about using McQuarrie as inspiration. So much so that the galaxy they've created there is too slick an clinical. Which is what his renderings were. As cool as the designs were, they were prototypes. And they still had that slick old school look to them. They weren't war torn at all.
It wasn't until production got their hands dirty, that things took off. And IMHO, that's when they made the human connection with the audience.
I guess I'm also a little bittr since they are severing as much as they can with the prequels. It's like everything has to be about the OT and they will suck it dry for inspiration. But at a certain point, Rebels will run out of Mcquarrie renderings to copy