Rey has definitely been challenged. She just deals with it differently.
Her entire life on Jakku was a challenge just to survive. Luke had an aunt and uncle with a home, food, and jobs, and he had friends. He even had a Jedi master watching over him, waiting to take him under his wing. Even though Anakin was a slave, he still had Shmi and even Watto seemed to treat him decently. He even had his own racer.
Rey was left alone, got captured by the First Order, mind probed by Kylo Ren, watched her friend Han get impaled on a lightsaber and her other friend Finn get his back sliced. Luke was negative about training her. She felt helpless as the First Order targeted resistance escape ships and Kylo refused to call them off. Yes, Luke and Anakin both experienced adversity and great losses too. I’m just pointing out so did Rey, but she faced her’s without family or a mentor. There are no force ghosts talking her through anything.
Rey has had plenty of reasons to give up but she simply just does not quit. I love Luke Skywalker, but he was very whiny. Anakin was too. Rey just sucks it up and gets it done. She makes it looks easy because instead of complaining, she gets straight to solving the problem. I don’t think Luke or Anakin would have survived long on Jakku alone with their attitudes. If you dropped a young Rey, Luke, and Anakin into the middle of a zombie apocalypse, I’d put my money on Rey being the one who survives and probably becomes the leader.
The Force enhances your abilities. Rey was already shown to be a proficient fighter just to survive on Jakku. Of course she defeats an emotionally distraught Kylo who had just been shot by a weapon that we’ve seen can send bodies flying. She knows a lot about mechanics and ships from salvaging, so I have no problem with her being able to repair the Falcon. There’s no training better than experiencing something first hand. Kylo probes Rey’s mind aggressively, so her being able to get inside a weak minded stormtrooper for a second doesn’t seem surprising to me. It would be more surprising if she just sat there and did nothing while waiting to be rescued. Her abilities are no more surprising than a small boy being the only human that can pilot a podracer or a rural farmboy flying a combat mission in space or blocking lasers with a blast shield down just from a suggestion to reach out.
A great deal of the Jedi training we see in the movies deals with focus. Luke and Anakin both lacked focus. Rey is extremely focused. She is strong willed and determined. She is task oriented and has a can do attitude. All of that can take you a long way.
I disagree that Anakin lacked focus. He was confused, yes, but that doesn’t mean he wasn’t constantly striving to become stronger in the Force, to become a master.
Anakin and Rey are actually very similar characters, where their formative childhood years are concerned. Young Anakin was a ‘Leave it to Beaver’ incorruptible child who saw the good in everyone, despite being a slave. This makes his descent into the Dark Side tragic, and really it’s the only way to make his character interesting. How boring would it have been if he had stayed the hopeful decent person he was as a child, never succumbing to the darkness all around him?
Rey is the answer to that question, at least so far. I’m sure some people enjoy this about her character, but for me it feels entirely undynamic. Thus her proficiency is a bit of a red herring because it simply masks the deeper issue that she doesn’t undergo the dramatic character change necessary to drive the story forward.