Many years ago, in a much less politically correct era, I worked as a college admissions counselor at a selective college.
At the time, the best predictor of college success was your ACT or SAT score, which basically told us how smart you are.
The second most important predictor was your high school transcript. We looked at the courses taken and your grades. Students who took math, science and language courses were favored because we knew they were willing to challenge themselves and had at least some study skills.
Most reference letters were useless. The exceptions were from a handful of teachers and guidance counselors with whom we had a history and whose judgement we valued.
We liked well rounded students who participated in band, choir, sports and other activities. We also liked to see work experience. But that was not nearly enough to get you admitted by itself.
I should add to my previous post: We were, of course, actually looking for the best students and only for students who could be successful in college. That part has changed.