- she performs tasks too easily and never experiences significant failures or setback
- she never has to suffer in order to grow, she just learns them on the fly
I disagree about the setbacks. Note that I don't write "failures" but "setbacks", the difference being that failures would be her fault, while setbacks aren't necessarily her fault. Han's death, her being captured by Kylo, and the revelation about her parents are setbacks, and I would call them significant, although I agree that they aren't displayed as impactful on her as they should be.
Kylo has been shown to be pretty incompetent. I hate that he is being touted as being naturally stronger than the likes of Yoda, Palpatine or Vader.
I kinda like that because it shows that strength isn't everything. Kylo might be stronger than any of them in a way (Luke talks of _raw_ strength, it isn't quite explained what he meant with that, but it might mean something else than we think, because the strength demonstrated by the other strong force users Luke met was way more impressive than what Kylo showed so far), but he obviously lacks training a lot.
I also think that is in line with Snoke's character as far as we have seen him. Snoke probably hasn't trained Kylo nearly as well as we thought, because even a force user with way less strength but real training (such as Obi-Wan) would defeat Kylo I think, perhaps even easily. Snoke knows how dangerous a fully trained Kylo would be. He wants to stay in control so he doesn't tell Kylo everything.
Kylo's performance in the fights we have seen in the movies shows that, I think. While you could argue that against Rey he cannot use his force powers well, since she is also very strong in the force (that's one possible explanation why force users battling each other throughout the movies don't use force powers _that_ often during fights), I don't really see the reason why Rey and Kylo performed so poorly against Snoke's guards.
I llike that scene a lot, for me it was one of the highlights of TLJ, but I mean, seriously: Yes, Rey and Kylo won the fight despite being outnumbered, but imagine Obi-Wan and Anakin fighting those guards.
Here's how a force user looks who fights non-force users:
Deflecting a blaster bolt back with his bare hands, choking and lifting a soldier to the ceiling while at the same time swinging his lightsaber deflecting blaster fire, taking weapons out of the hands of enemies, slaying trained soldiers left and right. Sure, those guys don't have melee weapons and they are scared to death, but I cannot imagine any but the most well-trained and equipped regular people (Jango Fett or the robotic guards of Grievous) to have any kind of chance against a moderately skilled force user with a lightsaber, unless they are at least at company strength.
Here we see Yoda and Obi-Wan fighting 15 or 20 Clone Troopers (elite soldiers) and during that scene we see both Yoda and Obi-Wan using the Force powers to do so.
If we compare that to Rey (who even swings her lightsaber wildy out of measure a few times, missing completely. Kylo looks quite a bit more proficient with the Lightsaber) and Kylo who seem to use the Force not at all during their fight with the eight guards that's what I meant with "a bit underwhelming". Rey and Kylo each kill four of those guards, but Rey kills three of them in one-on-one situations and one with a quick stab in the chaos of the first seconds, while Kylo fights three of them at the same time at some point. He has a bit of bad luck when his lightsaber gets stuck in the armor of opponents twice (the second time he even has to drop it do dodge a strike), but overall he displays great swordmanship there. Fighting multiple opponents is hard and the Praetorian Guards are (as we know from Kylo's view point in the TLJ novelization) the best fighters in the First Orders, and also wearing armor that helps against lightsabers. In fact the novelization tells us that Kylo is not sure if he could win against them.
So that says a lot about Kylo and Rey: They can use the force, but it seems their training doesn't allow them to do so in real stressful situations like in the middle of the fight.
Here's a compilation of all the times Kylo uses the Force in TFA, and it seems that while his strength is impressive, he needs to concentrate a lot on the Force, he uses it to quite some effect, but those are all situations in which he is confident and in control of the situation.
And by the way, Rey looks really bad against Kylo when they first meet. She shoots at him, and badly so to boot, and she is scared to death when he just deflects all her bolts, freezes her, even looks away from her giving commands while she is frozen (it seems he doesn'T have to concentrate a lot there). And then he just stuns her with the Force and carries her away. That's not exactly OP of her.
When they meet on Starkiller base he throws her against that tree like Obi-Wan would do with a combat droid. Not too impressive of her either.
I agree that her OP moments are a lot stronger in TLJ. But then she does have the old Jedi texts (no clue if she read them, probably not but probably she did, or at least was supposed to do so by the original screenplay before it was put into those tight time constraints.), a bit of training by herself and Luke (again, too shortened in the movie, which I really dislike), and most importantly a lot more confidence which probably helps if you are strong but don't know what to do with your strength.
Is she still an OP character?
Yes, I guess so. But not as wildly OP that it would bother me. A Mary Sue would.
The last point is her quick learning, and that is the one point I fully agree with. She learns REALLY fast, especially Force powers. Her mechanical skill, flying, and parts of her fighting skills are explained in the novels, her quick learning of force powers isn't.
Again, I do think that when watching TLJ and reading its novelization it is possible to see that some parts of the movie, especially the Ahch-To scenes, were originally meant to display a much longer period of time. Same goes for the Canto Bight scene, in which the characters seem to have a weird amount of time at their hands and don't seem particularly stressed about having to get back to the Resistance quickly.
And that's because the "fleet scenes" and the time constraints put on the rest of the story by them probably weren't meant to be in the movie in the first place, or at least not in that form.
I'd almost bet that in the original draft Rey was on Ahch-To for months and learned a lot about all the Force stuff. Not nearly enough, just like Luke on Dagobah she left before she should have, but she did receive a substantial amount of training. She trained by herself and with Luke. She also spent some time in hyperspace after that, and that's when she read all the Jedi books, unlike Luke who apparently didn't. Combined with what she ripped from Kylo's mind in TFA that would make a lot more sense, and that's probably my main point of critique about TLJ.
They probably felt they would add to suspense by having all of that happen within a few days, simultaneously, with the fleet being in danger, but IMO they were wrong. The fleet scenes were not only silly from a physics point of view (ok,ok, like all space scenes in Star Wars, so par for the course I guess) but they rushed the plot and thus contributed to the negative views on Rey's character development, among other things.
And one last point I'd also like to mention:
One might argue that learning a lot about the movie and filling plot holes of the movie by not actually watching the movie but reading the novels and playing computer games (Star Wars Battlefront story is canon for example, and has tie-ins to both TFA and TLJ) is not so great and the movies should stand for themselves, and I do agree with that up to some point, but we have to take into account:
That has always been true for Star Wars. We don't notice it that much because we have known the OT and prequels for many years, and most of us have probably seen the three movies of the OT together as one finished piece fitting together (unless y'all are significantly older than me), and there is loads and loads of information that is just "common knowledge" and not really in the movies, but stems from the mind-boggingly large amount of stuff the EU provides, or stuff like commentaries by George Lukas. If you only watch the OT by itself it is full of plot holes and lacking a lot of information.
Same goes for the prequels. The plot holes are even worse there, and the movies directly contradict the OT. Only the expanded universe, novelizations, computer games and all that stuff filled all the holes and put the missing pieces into place. Many things are only implied in Star Wars movies, and explained later in other sources. Star Wars has always been a cross-medial franchise, and thus I think it is not fair to use that as an argument against the newer stuff only. You are expected to read the books and play the computer games in order to have everything explained. I think they might have overdone it a bit this time, but overdoing something is the most important trait of the modern age I guess, so again that is to be expected. George Lucas is an expert in milking the franchise cow and Disney isn't any better, but that is Star Wars.
. That chestnut is getting too old and needs to be put down (should really have been put down after VI, but of course J.J. wanted to bring the so-called 'nostalgia' back). I wouldn't be surprised though if he does it again 
The last time I remember the Vader suit was worn by the British actor David Prowse - the only reason why he didn't voice the part as well was because he was from Bristol and they didn't want Vader to have a Bristol accent, which would have made him more of a comic villain than a serious one 
