In Style vs. Style fights promoted commonly online, it is usually a professional fighter vs. an amateur/hobbyist. One fighter clearly has more fight experience and is a different level athlete and pro level. It is clearly an uneven fight. You could place a professional at any level and put them up against a student of a different style with little experience and the professional will win 99% of the time regardless of the style.
If you want to compare styles, you need to compare fighters at a similar level. When you see high level, professional MMA fighters use Wing Chun in the cage, Wing Chun works.
If you see Wing Chun used in amateur fights vs other styles, it also works.
Here are 2 examples of Wing Chun vs. Muay Thai and Wing Chun Wins. Muay Thai is commonly combined with BJJ in MMA, since both systems are incomplete on its own. These videos show Wing Chun is an effective style against one of the most touted styles for MMA fighters.
Wing Chun vs. Muay Thai…Wing Chun WINS
Wing Chun vs. Muay Thai…Wing Chun WINS