Having the correct takeaway and shoulder turn to begin your golf swing is absolutely vital if you are to make a great swing.
The takeaway is the first movement you make during your backswing and as such it dictates whether you make a good, correct sequence of movements during your golf swing or not.
If you make an incorrect movement at the beginning of your swing sequence, you will be out of position and struggling to correct and regain the correct movement pattern for the remainder of your golf swing. If your movement and swing sequence is correct then you will hit solid, consistent golf shots, however, if it is incorrect you will experience inconsistency with your strike.
A good correct takeaway will see you making a correct shoulder turn to begin your movement. From your set up position, create a straight line from your left shoulder down your left arm to your hand and then down the club shaft to the club head. As you take the club away from the ball, you should maintain this straight line and move it to the right away from the ball from your left shoulder. Move the club head along the target line from your left shoulder until your hands are past your right thigh and then hinge your wrists so that the club head rises up from the target line. Continue to turn your left shoulder so that the club shaft rotates inside the target line and becomes parallel to it when at hip height. The club head at this point should be as high as your hands.
To check this movement, stand so that you can see your reflection to your right. Work on turning your left shoulder towards the reflection so that your left arm points directly at your reflection and the club head covers your hand position in the reflection.
This will see you correctly rotating your shoulders during your takeaway and help you to achieve the correct movement pattern to initiate your golf swing, helping you strike the ball much more powerfully and consistently.