they were supposed to be bad at it. that was the entire point.
Though I wonder why Kylo is so bad when a) he trained at the Jedi Academy and b) he's been working for Snoke for years. Apparently Snoke hasn't bothered to give him any training and is only going to start now (?!).
Kylo really sucked. He was taught by Luke and he obviously retained none of it. Finn clumsily kept up with him and he never had any lightsaber training. I still say the battle looked like two kids playing outside acting like they were playing swords or in this instance lightsabers.