That's the other thing too... getting good groups with 3-dot sights can be a lot more challenging than with target sights, and considerably more difficult than red dots.
My opinion has always been that less than 10 inch groups is more than acceptable out to 20-25 yards unless you're specifically shooting for accuracy with the appropriate firearm.
Not to make any Lieberals nervous, but I train for "proficiency" (accuracy and speed) in case self-defense with a firearm ever becomes necessary: if you can hit center-mass groups out to those distances at a reasonable speed, you're doing perfectly fine in my opinion.
Your mileage may vary, of course.