Golf is a flinging activity, and what I mean by that is we’re flinging a weight at the end of a stick. If I asked you which lever was your last lever to fling with, the answer would be your wrists. The hands’ job is to hold onto the club, but you release with your wrists.
If you’re a puller, which means you’re dragging the grip faster than you’re flinging the club, your wrists are going to back up through impact versus releasing through impact. That’s not only going to make it harder to hit it straight, but it’s also going to slow down your clubhead speed down incredibly.
You have to learn to use your wrists, free your wrists up, and let the club fling fast from your wrists.