The reality is that how a player holds a golf club is critical to his or her ability to influence it. In order to apply forces to swing the club and control the club face, a player must have a functional grip. A poor grip is a (perhaps THE) leading cause of amateur struggles.
The key word, however, is FUNCTIONAL. There are many different types of grips, lots of preferences, and popular styles that vary amongst instructors. But functionality is paramount. To keep it simple, a “functional” golf grip means being able to physically hold onto the club under speed (no slippage or twisting), creating leverage (to develop speed), and controlling the club face throughout the swinging motion (especially at impact).
I work with students on grip when it needs to be altered for the player to meet one of the above requirements. But I also make sure to only work on the golf grip once a player has built trust with me is is committed to improving. A grip change is a big deal and can take several weeks to truly get down. And much like learning to hold a musical instrument, you must get the details correct. But the payoff is almost always worth it.
A good grip doesn’t guarantee a successful golf swing, but you’ll rarely see a good player with a bad grip.