When attempting to measure skill and experience, one of the things that martial artists (and combat athletes, to a lesser degree) tend to turn to is "time in". Even people who don't have any training will often assume that the amount of time someone has studied is somehow indicative of their skill. If I had money for the number of times when someone has said to me "wow...you've been doing Muay Thai for ten years? You must be really good!", I'd never have to worry about working again.
But the truth is, while time and skill are related to each other, they aren't perfectly matched up. I can think of several people at Sityodtong who, despite being at the gym for less time than me, are just as skilled (if not better) when it's time to throw down.
Now, in some cases, some of that accelerated skill is actually a time issue. Martial artists tend to measure training time in years, but that model actually ends up working very badly. Rory Miller gives an excellent breakdown of why in this post, so I won't bother trying to recreate it. Just go read it.
But there is more to skill than just time spent in training.
For one thing, there's a question of how you spend that time. On any given day at Sityodtong, I might see as many as fifty students pass through the doors. Maybe more. A single class might have thirty students in it. Those thirty students might all train for the same hour, but they do not all use the time the same way. Some of them come in focused; if there is something they suck at, they do reps of it until they stop sucking, and then keep doing reps to make sure it sticks. When the bell goes off for bag work, they put their hands up and treat the bag as an opponent for three minutes. When doing a drill, they close their mouths, open their eyes, and go do the drill. If they don't get it, they ask for clarification. Then they keep drilling.
Other students don't do this. They chat with their friends while jumping rope. Or during technique. They hit the bag randomly, not thinking about what they're doing. When a trainer gives them feedback, they ignore it, or follow it for a minute or two, until they're bored.
Both groups are getting the same amount of training time, but one group is going to get better significantly faster.
Even beyond all that, however, there are other factors. Some people are just natural talents. Others aren't. I think of myself as being closer to the latter category. I do not pick up new skills quickly. I need to drill them, experiment with them, play with them, and above all else, do a lot of repetitions of them. Eventually, stuff clicks, but it takes time. Depending on the skill, some things take longer than others (I have a lot of practice hitting people, so new concepts about how to hit people come quickly. New movements on the ground tend to take longer.).
Some of my teammates are phenomenally talented. They can see something and replicate it within a few repetitions. I don't know why. Maybe it's psychological. Maybe it's genetic. Whatever it is, it lets them learn stuff quickly. It's just the way they're wired.
All of which is to say, the only thing that really measures skill is skill. Time in matters, as does physical fitness, mindset, and a whole lot of other things, but at the end of the day, you're as good as you are. Neither the universe nor your opponent cares how much time you've put in, only what you can do.
But the time does help.