You know Luke got about 10 minutes training from Obi-Wan and about a week from Yoda, right? Yet he's a Jedi Master by the end of ROTJ.
Rey could already fight/handle herself in Force Awakens (we see this on Jakku) and Luke was just a Farmer who was a good pilot. For all we know he never had a fight in his life before meeting Obi-wan.
You're wrong. Let's take a closer look at Luke and consider the movies.
Luke had a brief introduction to the force by Obi Wan after never doing anything with it at all - remember this was the first ever Star Wars, this introduction was for both Luke and audience's benefit to get an idea of what it is. We're given context about the past, where his lightsaber came from, what the force is, what the Jedi were etc.
After taking his initial steps in the force with Obi Wan, he faces his first trail during the destruction of the Death Star. He gave up on his worldly senses and allows the force to work through him "Use the force Luke." Step one.
Now opened to the force, lightsaber grab in the snow cave, he is then sent to a Jedi Master who trained Jedi for 800 years. There he learned about the force in more detail for an unknown amount of time. We're given context in why he needed training "Control, control, you must learn control!" We learn that Jedi are normally trained at a much younger age due to the dangers of it. It's established in Empire Strikes Back itself that he's not ready, he has a way to go before he can be considered a Jedi. He goes up against his enemy and gets battered, not just physically but emotionally aswell. Even Darth Vader starts training him in a sense. "Impressive. You've controlled your fear, now release your anger." All of this is context in story telling and character progression. The audience follows Luke's progression. Step two.
Time passes, he constructs his lightsaber and during this time its "safe to assume" given what we know he's already been through and learned that he's now more in-tune with the force. There's a justified air of maturity about him. He senses conflict in his father, the light in him, and ultimately faces his ultimate trial. Also you have to understand that Vader didn't want to kill Luke, he never did, it's the entire point of the original trilogy. It's about family. So it's not like he was going up against a Sith hell-bent on destroying him. Both the Emperor and Vader wanted him to join them. That's a different type of threat.
Luke overcame his ultimate challenge as a trainee Jedi and defeated the Sith not by using martial power (despite overcoming Vader by tapping into the darkside when Vader baited him with threats to his sister) but by relying on his insight and belief in the light he felt in his father. Its only then he becomes a Jedi knight. Yoda himself tells us this.
The context is there, the progressive story steps are there, the character development is there.
Now imagine if Luke had left Yoda, went to Bespin and beat Vader. That really wouldn't work, infact it would ruin the whole thing because Vader then becomes pathetic and Luke is a super power for no real reason despite having been trained by Yoda and Obi Wan. Rey goes a step further than this by having no training at all and is able to do many things with the force instinctively and fighting to the death with trained elite warriors. Granted this would be fine, something new if the story developed her character and showed us WHY it was this way, but it doesn't establish anything at all. It leans on the old rules and at the same time ignores them. It's confusing, lacks context, has no depth and no sense of character progression. It's **** story telling.
