Let's take a look at Luke Skywalker:
Luke leaves with Obi-Wan, Han, Chewie, R2-D2 and C-3PO for Alderaan. He gets like half an hour of lightsaber training consisting of deflecting blaster bolts.
Then they're captured by the Death Star and Obi-Wan dies. Then Luke blows up the Death Star and three years pass before Empire where Luke is busy doing Rebel stuff.
Cut to Empire.
Luke has gotten a little bit better with the Force (despite having no one to train him) since he can call his lightsaber to him. He's still really clumsy with a lightsaber, only using it to cut things rather than having any finesse. He goes and meets Yoda.
Yoda trains him on using the Force, teaching him to levitate objects and such, but notice how there is absolutely no training with lightsabers. In fact, when he enters the cave, Yoda specifically tells him to leave his weapons behind.
Yoda didn't give a crap about lightsabers. He was trying to teach Luke something greater. He was teaching about the Force being more important than physical strength. "Wars make not one great."
Then Luke leaves, gets the crap beaten out of him by Vader, and a year passes. During this time, Luke constructs his own lightsaber, but does not go back to Yoda for training, nor does he have anyone to train with.
Luke rescues Han, and goes back to Yoda to complete his training. Sadly, he's too late, and Yoda dies from old age. Before he dies, Yoda tells Luke that he doesn't need more training, andconfronting Vader will make him a Jedi.
Apparently Luke will become a Jedi due to the will of the Force and when it deems himworthy, not due to how many hours of training he put in.
Luke then goes and beats Vader by tapping into the dark side, but ultimately rejects it.
So to summarize: The most lightsaber training Luke had throughout the original trilogy was a quick half hour session deflecting blaster bolts.
Yet he still managed to defeat the Dark Lord of the Sith, who had years of experience.
Because he was strong in the Force!
His usage of the Force to guide his actions was ultimately what allowed him to triumph over Vader, not lightsaber training or fancy form usage.
So why on earth is everyone throwing a big stink over Rey doing the exact same thing?
We even explicitly see her stop, calm her mind, and open herself up to the Force!
Apparently this is enough to take out Vader, but not Kylo Ren, who was:
- extremely conflicted throughout the film, even more so after killing his father
- badly wounded from Chewbacca's bowcaster
- extremely out of practice in lightsaber fighting given he was the only one carrying one for quite a while
The whole point of the Force is that it has a will, and that tapping into it is what gives a Jedi their power, not how many level-ups they've gotten or how good they are with a lightsaber.
So why is this a problem?