I developed a huge dislike for the prior head pro at my current club, because of a couple of arrogant instances that I took issue with... which aren't worth rehashing here. He's no longer there for various reasons. But I will say this much about him - he gave me the best 20 minute lesson on the practice range a few seasons back.
And I say this knowing that we all struggle with different things in our swings, different aspects of the game.
But I went from driver being the most reliable club in my bag to suddenly flaring shots out to the left, or coming over the top with a shut face and pulling the ball to the right (I'm a lefty). No idea why. Alignment was good, posture was good, ball position was good.
He watched me hit about a dozen 7-irons, and I was hitting them very close to the 160 yard flag. He then tells me to hit some shots with the driver. After about 3-4 minutes, he stopped me. "With the shorter clubs - the irons - you keep the club much more on-plane. There's absolutely nothing wrong with your iron swing. But you need to swing your driver the same way."
And I struggled with that concept most of my life playing golf. The iron swing is nothing like the driver swing. The ball is not on the ground, it's sitting on a tee, and it's obviously much more of a sweeping motion than a descending impact motion. I think we all agree that taking a divot with a driver usually ends up being a disastrous result.
But he corrected my thinking. "When I say I want your swing with the longer clubs mirroring the swing with your irons - I'm not talking so much about impact. I'm talking about the backswing. When you hit those 7-irons, your right shoulder didn't drop when you took the club back. It just simply rotated under your chin. But when you hit driver, you drop your right shoulder, the club comes back way too much to the inside, and you either hit a block or a pull, because your natural instinct is to try to square the face at impact. Sometimes it works, most times it doesn't. Just focus on keeping your right shoulder level as you take the club back, just like you do with your irons."
And in modern day teaching instruction, what he was basically saying is keep the club lower to the ground for a bit longer during the takeaway.
Best lesson ever in all my years of playing. And it took him 20 minutes to spot it, and it took me all of 5 minutes to apply it. My once-reliable tee game that had abandoned me was back again.
Now had he told me, "don't bring the club back inside so early" - I never would've felt the connection of what he wanted me to do. But "keep your right shoulder more level on your takeaway and allow it to simply rotate under your chin" - it was an "Eureka!" moment for me.
A lot of times we just need "simple" instruction, vs the "don't do this or don't do that."