wing chun is basically taught as a "self defence" art, a way both men and women, big and small people can use their body to its maximum efficiency to defend from a persons attack, the eye gouging, knee breaking and stuff its about that. It follows on if you are attacked by somebody (on the street), anything goes so you should use "anything" in your power to take the guy down. Of course this has no application in MMA leagues, however even without the illegal moves wing chun can still be (on paper right now) a good striking art in organized mma fights, just like all striking systems can be, all of them depend on its user not the style everyone always tells me

"A wing chun master is just gonna be taken down by a jiujitsu guy and pounded"

or

"there were wing chun masters at the start and they got their butts kicked"

of course if they only know wing chun they probably wont get far, thats why its MMA you can learn wing chun and jiujitsu and it will better your chances.

and the wing chun masters at the start probably didnt have alot of experience with organized fighting, wing chun is not especially known for its competetivness.