Star Wars - The force, it, it's got a lot of power

Addressing some points...

Rey. She's not perfect. In The Force Awakens, she was far from a perfect pilot and crashed the Falcon into the ground multiple times, she was the only person to not see through Finn's lie about being from the Resistance, she was the sole reason for the Rathtar mayhem because she screwed up and pulled the wrong door fuses, one of the few times we see her using a blaster she misses (though hits soon after), she's also then captured shortly after because she was having an emotional breakdown in the forest. Then in the Last Jedi, she fails to convince Luke Skywalker to properly train her and come back to the Resistance with her. She believed she could stand up to both Snoke and Kylo on her own, but also turn Kylo away from the dark side (remind you of anyone?). She fails miserably and ends up destroying one of the most significant lightsabers in history in the process. If anything, The First Order is now commanded by someone who is clearly quite unhinged.

It also makes more sense that she is progressing faster than Luke Skywalker. When it comes to combat, Rey grew up in a dangerous society all alone, where scavenging valuable parts is how you make your living so it's only natural she has spent years training herself in close-range combat with her staff. Luke grew up on a farm, and (at least so far in canon) rarely had to defend himself in a close-range. With this context, it makes sense why Rey is able to adapt faster to using a lightsaber (which you will notice she has her own particular style that is evidently influenced by her accustom to a spear) than Luke. Luke seems to be much more capable with a blaster though, as we see Rey stumble with one in TFA.

When it comes to becoming one with the force, it's very heavily reliant on how you approach the Force, how much you believe in it. Remember when Luke is struggling in TESB to lift the X-Wing and admits its too big? But is then shook when Yoda, this tiny green frogman, lifts it with seemingly no trouble? Yoda states that the force is much more about understanding of the relationship between everything in the universe than it is about size or ability. Luke grew up never hearing of the Force, and when it is introduced to him he’s brash, impatient, reckless, and doubting, both of himself and of the Force. If Luke truly believed in the force properly, he would've been able to. We see this in A New Hope where with Obi-Wan's guidance, he briefly believes in himself and the force - this is shown by him turning off his targeting computer - and uses the force to help guide the missiles into the Death Star.

Rey on the other hand grew up hearing all the heroic stories of the Rebellion and the Jedi. Notice how in The Force Awakens she's flabbergasted when she realises that's the Han Solo right in front of her? How she knows about who Luke Skywalker is already and what he means? Meeting Han, him telling her it's all real and coming face to face with Kylo Ren all but quickly confirms all these stories she's heard growing up, thus she already believes in the concept of the force and it's relationship to the world. That's why her abilities developed seemingly so much quicker.

Kylo Ren. What he wants evolves between the films. In The Force Awakens, he wants to live up to the legacy of his grandfather and to be treated in the same way he was. We see this by his utter obsession with Darth Vader and the fact he models himself after him, the fact he wants to finish Vader's legacy by hunting down the rest of the Jedi. This continues early into the very beginning of The Last Jedi, until Snoke belittles him and his mask. Immediately after that scolding, in a fit of rage Kylo Ren destroys his helmet, visually symbolizing the end of his desire to become like Vader. He has come to realise that these old concepts of the Jedi, the Sith, the Resistance, The First Order, it's all pointless. History is just repeating itself over and over again (an important point in the entire story of the Star Wars saga actually). Therefore he sees fit to put an end to it, not just one side but it all. He sums it up in one of the films most well known lines "Let the past die. Kill it, if you have to" when he's trying to bring Rey to his cause.

Snoke. I think people are placing too much emphasis on him, expecting another Emperor Palpatine character. I'm actually really glad they killed him off because otherwise 9 would be too close to 6, and it added for an excellent twist IMO. In the film, Snoke essentially replaced Han Solo as a father figure for Kylo Ren. Throughout his youth, both Han and Leia were still active in their busy careers which often led to strong feelings of abandonment in Kylo. Snoke used this to his advantage to begin seducing him towards the dark side, but the ultimate tipping point was what we saw in The Last Jedi. Kylo Ren is a character who believes he has much more to himself than other people believe he does. When Snoke brutally chastised him at the beginning of The Last Jedi, retracting his faith in Ren, calling him weak and foolish like his late father (who Kylo was still conflicted over killing) and going as far as to claim Rey could be the one to fulfil Vader's legacy of destroying the Jedi. This was pretty much the breaking point for Kylo Ren and is the turning point he starts to fulfill his ultimate goal. So I sort of like to see Snoke as being the character that provokes Kylo to fulfilling his ultimate destiny.

Phasma. Yeah a disappointing waste of such an awesome looking character. Ugh she had a lot of potential. Reminds me a lot of Boba but at least he brought Han to Jabba.

General Leia flying in Space. She's not only been told of the Force all her life, but she knows firsthand of its powers from Vader and Luke, and was in a desperate situation in which her only latent Force powers she knows she has can save her. It wouldn't have taken a huge amount of push either, with the momentum in space. I'm sure being a direct descendant of the Chosen One helped too. Can definitely see how it looked silly, but it's not unfeasible.