In fairness, UFC fairly severely limits what can be done. To begin with, they use gloves, and things like eye gouges and finger locks are illegal.
Because strategies like "ripping out someone's intestines" are illegal, boxing and wrestling have an unfair advantage because they don't have to worry about that stuff to begin with. For more realistic fighting situations, see: https://en.wikipedia.org/wiki/Lei_tai
The eyes are small targets. The only time you can reliably gouge them is when you're already winning a grapple, at which point it's superfluous. Finger locks are similar, with the additional disadvantage of being less likely to end the fight even if successfully applied. Admittedly, UFC rules now also take entertainment into consideration, but early UFC rules mostly just banned things that risked permanent injury for very little tactical benefit.
Because strategies like "ripping out someone's intestines" are illegal, boxing and wrestling have an unfair advantage because they don't have to worry about that stuff to begin with. For more realistic fighting situations, see: https://en.wikipedia.org/wiki/Lei_tai