The simple answer is: YES, the Star Wars ships DO have too many greeblies. It's as simple as that. You can rationalize it all you want, but the answer is the same. There simply is no reason why anything would ever look like that, except that the model builders wanted the ships to look "interesting". Nothing would ever have that much random non-sensical detail. Not in the real world or a galaxy far, far away.
Han Solo made a few special modifications himself? The Falcon is more modification than it is original spacecraft. The thing just wouldn't fly. The only ship that makes sense is the Y-Wing, in that it's exterior had been removed to access the unreliable innards for service.
There's a notion in design, that "form follows function". When you look at Star Wars, and most science fiction films (models, costumes, and sets), there is so much detail that has no function. Not even fiction can account for all that detail. It's just too much!
When it comes down to it, no matter how much you like it... No matter how much you'd like to defend it... It's still just a movie. I have an MPC Falcon that I want to build to some degree of accuracy, but every time I look at it, I can't help but think: "This is just too much, and almost none of it makes any sense!"
So, in closing: It may be interesting to look at. It may be cool too. But yes Virginia, Star Wars ships do have too many greeblies.