I'm confused! I have question on Count Dooku, Old Ben, Mace Windu, and Palpatine?(Star wars)?

Ben was out of practice. It's not like riding a bike, you don't go 15+ years without using your lightsaber and just pick it up again. Also, he might have been capable of doing all those things, but he didn't want to kill Vader. Maybe he knew all along that Luke had a chance to turn Vader back to the good side of the force.