Go shoot a match. Nothing says you have to be competitive at the national level to enjoy the sport. The only thing you really have to compete with is your own best score. If you move through the stage a little slower than the Master shooters, but still have a good time and hone your skills, its a successful match!
FWIW, you might also consider Steel Challenge - lots of shooting, not so much running. But whether you opt for USPSA, Steel Challenge, IDPA, or Cowboy shooting, just get out to the match and shoot!