There are a thousand reasons a player could be hitting the ball poorly, but I think one thing that’ll help most golfers is a one-piece takeaway where everything works together. To practice this, setup in 2 steps:
1) Take your regular setup with hands dangling out over your toes
2) Leaving your right hand where it is, pull up on the club with the left hand until the butt of your club is touching your stomach, right by your belly button. You should still be in your setup posture. Remarry your left hand to your right hand so you’re gripping down on the shaft.
Once you get into this position, try starting your backswing. If you’re very armsy, the club will immediately detach from your body. Let the shoulders, core, and hips rotate with the arms to bring the club back so it stays attached to your stomach. When the club is nearly parallel to the ground, you’ll see the club still very much in front of you with lots of body and shoulder rotation. I think that’s a great feel, drill, and visual for most golfers.