I was a ~15min 5k/31min 10k runner in college who was mostly plagued by injury post-college. I'd go through boom/bust cycles of solid training then nagging injury with no good results. I should have started cycling earlier but didn't until my mid thirties, by which time I was 40 lbs overweight.
Road cycling seemed very intimidating both in cost and it seemed kind of douchey (to an outsider at least), so I dabbled in mountain biking. After a few years of crashing into trees, a friend turned me on to cyclocross, so I bought a bike to race the local CX series. I was terrible at bike handling, but having fun. It rekindled my competitive spirit that had been missing since college. I went all-in and bought a road bike and subsequently won my first cat 5 road race.
I'm now mid forties and have been racing cat 3 for cyclocross and road for the past six years. I'm not great but not bad. I've won a handful of races and been DFL. My bike handling has improved so that I can hang in most crits, but I mostly chase primes or try to stick in breaks. You'll never find me in a field sprint!
What I enjoy about the sport is that I can push myself hard on weekday group rides, follow up with hard intervals on the trainer, and still have the ability to do long rides on the weekend. After hard training blocks I am usually rewarded by higher fitness, not injury or chronic soreness. Running was always a battle to stay injury-free. I don't miss that at all!