Full disclosure: RacerEx is my coach.
The strongest guy, the most genetically gifted guy, the most determined guy, none of those are predictors of race success. Sure, a freak or two comes along every year and rips through the lower categories and then hits the wall of their capability. The ones that continue to succeed at the highest level are rare. Most of us are not freaks, so we work our way up using all of the skills required to succeed at racing at the highest level. There is no single factor that can determine success.
So why are you considering racing? What is inside that drives you to try it? Fun? Socialization? The challenge? Demons in your past? A boring life? Some or all of the above? Finding those honest answers will help you drive your expectations, and expectations are the most important part of the mental game of racing, which I consider to be significantly more difficult than the physical aspect. For me it's an order of magnitude more important. Not so much for beginning racers but as you gain more experience the importance increases.
Quid pro quo. I started racing in 1981 while I was in college. I had ridden a drop bar bike for years as a kid and worked part time at a bike shop in Boston. I used to ride with a group of college kids at night and on the weekends. One of them was a Cat3 and encouraged me to race. I lapped the field in my first race for the solo win, and twice with another rider the next week for my second win. I was a Cat2 in two years and raced on one of the most dominant teams in the Northeast that spawned multiple National Champions and pros. Then I got burnt out and quit. For decades I noodled around on a bike but my race bikes gathered dust. In 2009 I had a cardiac event that turned out to be a false alarm, but it was a wake up call. I hit the gym and changed my diet. Running in the treadmill was killing my knees so I sold my vintage stuff and bought a race ready bike. I lost 35 pounds and returned to racing at age 52. I placed 12th in my first M45+ race and since then have won many regional and a couple of national races as a Master. What drives me? Staying in shape. I am naturally competitive and I am good at this sport. Winning, there's nothing like it. Beating people with stronger palmares and kids half my age. Sharing knowledge with new racers informally and formally through teaching clinics and mentoring. I am also a USAC official, which is a topic all to itself.
Find what drives you, and you will find the answers. Best of luck and don't be a stranger.