While 85-90% of all cadets have played a high-school sport, and lettered in it; only a small percentage were "Captains" of those teams. Most people need to find leadership experience in other areas. President/leader of a club, class officer, boy/girl state, drum major, section leader in band, etc... There are plenty of places to get leadership positions. The academy also wants volunteer time too. There's a lot of room to demonstrate leadership in volunteer activities. Coordinating and running a volunteer activity.
Bottom line is: People need to learn how to assess their own accomplishments and abilities. Most people have a lot more accolades than they realize. People have a lot more achievements than they realize. Unfortunately, many are looking for a magic checklist that gets them an appointment. It doesn't exist. Neither can anyone here spoon-feed anyone the right answers to your concerns.
On the same note, there are a lot of people who have no leadership accomplishments. They don't naturally excel in their activities. They are traditionally "Followers". Sorry, but you can't just become a leader over night. You can't look at some list and try to fill in the blocks.
Here's my suggestion for the activities you want to include in your application.
1. Do ALL of the things you enjoy doing; and excel at those things to be the best.
2. Those activities you are involved in; try and be in charge of some/part of it.
3. Make your life as challenging as possible. Most challenging classes, activities, sports, spare time, etc...
4. Be as well rounded as possible.
Unfortunately, there's a lot of people who don't like this type of life. They don't want to be so "Multi-Tasked". Then don't think they have enough time in a day. Then, when they get to the academy, they realize that the military really does want this type of person. Just people who have quit, there are already more than 25 in the current class of basics. This isn't including injuries. This is just those who want out. And the list we grow even more. Too many people don't know what they're getting into. Just because a 16-17 year old says they WANT to go to the academy, doesn't mean they should go to the academy. If TEAM sports/activities interest you more than individual sports/activities, then the academy/military is probably for you. If you understand the need for rank; for people to tell you what to do; for doing what you're told, and not doing it necessarily your way; then the academy/military is probably for you. This isn't to say the military wants robots. On the contrary. They want individuals who can think for themselves. But they need to realize that they are just a PART of something much bigger. They need to lead their part, but must be able to follow those in the parts higher than them.
That's what the whole leadership thing is about. The academies/military is not meant for the "ME-Generation". It's meant for the person who considers the education, benefits, pay, travel, medical, etc... to all be secondary to the primary purpose. Which is to be part of something bigger than yourself; in the combined defense of our constitution and to maintain peace. Which could include risking your life. Not saying that you should be willing to join the military without any type of pay or compensation. That's foolish. But you have to look beyond what's good for you, and look at what's good for the military and our country.
So don't try comparing club leadership with being a captain of a sports team. You're trying to fill a square on a checklist. Such a checklist doesn't exist. And no one here can spoon feed anyone else what they should be doing. "Be TRUE to Yourselves". If what you are doing and wanting to do is in line with what the military wants, then it will become clear. If what you want isn't in line with the military, then that too will become apparent, and maybe the military isn't what you were meant to do. "BE TRUE TO YOURSELF". That's more important than ANYTHING ELSE.