In building a wall, if one simply focuses on repairing the breaches, but doesn't spend time shoring up defenses and making the entire wall stronger, the wall will break down everywhere. How does this apply to raising children?
Take the time to analyze your child's strengths, give praise and think of ways to make them stronger. What if Mozart's parents had not allowed him to pursue music and had forced him to work on a weak skill? What about Einstein? Or Alexander Graham Bell?
Dave Ramsey was saying that when we work on weak areas, we generally only make them mediocre (we should still work on those areas, we can't ignore them), but how wonderful would your child be at a particular thing if we let them focus on their strengths to make them extraordinary?