The big no behind the vong really to me at least is that it's doesn't fit the theme of Star Wars. They never have.
It's not that they don't fit into SW, it's that the way the were written and portrayed doesn't fit into SW. The idea of an alien threat that is resistant to Jedi and bent on "reconstructing" the galaxy for their own purposes is very Star-Warsy. It just the lazy writing and "they can beat anything!" mentality that was the problem. Kind of like how Mandalorian culture, and all that stuff was pretty cool until KT basically made them the perfect society where everything always works out.
The concept of the Vong wasn't the problem, it was the execution (not to mention the fact that 19 books written by a multitude of authors is gonna screw up somewhere, and it just so happened to be the first half of the series that was bad)
