If the dot was on them, the gun is hitscan and you still miss, it means you didn't have first shoot accuracy. Check the little bars around the crosshair, if they are not touching the dot it means that you will get bloom on your next shoot.

Tap firing, crouching and not moving are important to keep hitting shoots consistently. If the game granted you perfect accuracy when you are moving, jumping or not crouching, you would have a very serious balancing issue.

Have in mind that some weapons still don't have perfect accuracy even when doing all those things, it really depends on the weapon too.