I said skill/attribute.
You have other attributes like speed, durability, pace, fight IQ, heart, ability to pick up techniques that all fighters have at varying degrees.
If one guys is a grappling phenom, that's an attribute he has. Another has a great chin, another blistering hand speed, another a great mind for analytical thought.
All of these are attributes/talents/skills that make a fighter able to do stuff others can't. Life's not "fair" - even a really powerful mind and work ethic can be viewed as a skill, an ability.
And size is such an attribute, and one of the most important ones too. Are you a small guy? Tough shit, you'll never be the best fighter in the world, just as you won't be able to dominate in basketball.