that's a bit of an unfair assessment, do allow me to explain :-
G&G quality is really really good, very rarely do you hear of one going wrong, and so confident is G&G they offer a 2 year warranty, most other manufacturer offer a year.
But like you say they are common, and there common for a reason, there good and they do work well, out of the box.
i suppose i am a little bias, i do have a CM16, which i never opened until it was over 2 years old. it is a great gun.
you could argue that TM plastics are better, but they at the least twice the price for not that much better (i own a TM MP5K too).
i will grant you that TM hops are better, but not by much real world distance.
don't get me wrong i am not saying that there perfect, but they are very consistent, very affordable, and they do what they say they are going to do, and they are easily up-gradable.