Part of the point of a good protagonist is that they aren't perfect. They can fail. Even comic book heroes have vulnerabilities and weaknesses. Watching the character overcome those weaknesses, struggles, and failures over the course of the story is what makes the whole story worth watching. That's basic character development you learn about in a high school writing class.

Like I said, Luke trained and trained and trained to learn how to use the Force. It didn't just come to him. And he got in trouble and needed to be saved and rescued by Obi-Wan more than once.
With Rey, she gets captured and can all of a sudden out of the blue perform Jedi mind tricks (literally) to get out of any situation she's in. She can suddenly call the lightsaber past Kylo Ren and know how to use it.

She will be revealed as one of the Jedi Students at Luke's Academy that Kylo Ren soured and destroyed. She would have been very young when she was transplanted into the desert wasteland of Jakku.
Maybe her memories were suppressed and contact with the Lightsaber ignited them. Hell, Obi Wan's force ghost talks to her when she touches it. Calls her by name (this is confirmed, they edited Alec Guinness saying the word 'afraid' to change it to 'Rey', the rest of the sentence is said by Ewan McGregor's Obi Wan).

And it's not just Rey. What exactly made Finn change? All it took was his stormtrooper buddy getting shot? That's it? The plot appears lazy. The characters have no depth. You really don't feel much for any of them, even the villains. The First Order, Hux, and Kylo don't have the same evilness and sense of dread you felt with the Empire, Tarkin, and Vader.

And it's the same recycled plot of Ep 4. They had a planet-killer weapon with some major vulnerability that the Resistance is able to easily attack and destroy the whole damn thing. They even had a droid carrying a secret message for the rebellion! The future Jedi hero is on a desert planet unaware of their destiny. It's all been done already. Did JJ Abrams get messed up and thought he was doing a reboot instead of a sequel? I've seen A New Hope dozens of times since I was a kid! I wanted something different. What's Episode 8 going to be about? Will it copy Empire Strikes Back? They might as well call it First Order Strikes Back!

One other problem with the plot...they destroy five planets with their weapon. But they don't destroy the planet with the base? Isn't the common sense strategy of war to take out the defense capabilities first? Who the hell destroys the Senate before the military?

I know Disney just wants to make some money. But geez, they could at least come up with a new idea or some characters with more depth.

They do address Finn. Children are taken from their parents at birth and pulled into the storm trooper ranks for brainwashing. 'Finn' is on his first assignment and revolts knowing it's not him and he won't participate.
Is it a bit of a rehash of the original Star Wars? Absolutely. Given that we haven't had a decent Star Wars movie since 1983, I'll accept it. The prequels were an emotionless computer generated documentary on the Uncanny Valley. There was no danger, no stakes, everything looked sanitized and saccharine. At least with this one, I can buy into character development. This is a series built on the old Rocketmen/Buck Rodgers serials and I welcome the new chapter. The prequels were devoid of life and excitement

Same reason every movie with a McGuffin doesn't end without it being solved. It's the adventure.