Why does everyone call Luke from the movies a Mary Sue?
His main accomplishment in the first movie happened because he spent his free time flying through canyons shooting very small targets for fun and got good at it. He had a lot of difficulty with the Force, and only used the Force (which in ANH was different to some extent from the Force in other movies) at the end to basically zen out. Han also had to save him in the trench run.
ESB, Luke still has difficulty with using the Force, screws up his training, and ends up being beaten by Vader.
RotJ, Luke beats Jabba by having a back-up plan coordinated with Leia and Lando and dependent on them . His initial plan failed because Hutts cannot be mind tricked. Luke goes to fight the Emporer, and fails. He goes over to the Dark Side briefly and even when he returns is no match for the Emporer. He is only saved because he brings out the remaining good in Vader, who kills the Emporer for him.
Luke in the movies just barely beat an emotionally conflicted Vader, was unable to beat the Emporer, and showed par-for-the-course Force usage.
There is no strict definition for Mary Sue. The term is applied to a wide array of characters in fiction, but with regards to Luke the explanation lies in that he is powerful because of his blood. This is a trope that you see in a lot of Fiction. Take Harry Potter for example. It is easy to write your character to be the only one who can save the Universe when it is mainly due to your powerful family. And it's boring.
Being a Mary Sue doesn't mean you cannot have problems or trials. Superman is still a Mary Sue even though his weakness is Kryptonite.
Luke can shoot Womprats or fly around in his little Speeder on Tattooine, but that does not make him worthy of the being the sole individual who can save the Universe? And the characters in the film routinely tells us that Luke is the hero. The spin of this in the prequels is of course that, it's actually Darth Vader who is the hero. He is the one who brings balance into the Force. He destroys the Jedi Order and the Emperor in the end. Luke is a text-book hero. He is so good, kind and heroically good all around. His only flaws is that he listens too much and works too hard.
Darth Vader and Han Solo are more nuanced characters. Darth Vaders story is about redemption, and Han Solos is about Apathy. There is a much stronger character mentality shift than for Luke who remains the good guy he started out as at the end. That naivity Luke has, in the beginning, is still the sort of idealistic determination he brings to the end, and that is proxy for Darth Vaders character development (killing the emperor).
I don't think we should use a Mary Sue is a derogatory term, but I do think that Mary Sue characters are easy to write and that they lack the fundamental dramatic shifts of more flawed characters. Mary Sue characters are a major problem in super hero comics and fantasy fiction where they are also depicted as powerful beings with a few inserted kryptonite moments added in.
Sometimes you'll have interesting takes on the Mary Sue formula. Aragorn in the Lord of the Rings is tormented by his family blood. He has a long lifespan and is seen as being more powerful than normal men, but at the same time his house is credited with being weak to the influence of the Ring. Or in Naruto it is explained to us that Naruto is a descendant from a powerful house of Ninja users, but his power is also derived from the beast within him. Kishimoto writes this beast to also be a burden that can kill him, and hurt his friends. Both characters also fit under the Mary Sue umbrella but have their own spins on it.
I don't mean to say that Luke is a bad character. But I did find him boring by the end. I did find him too good- Like a Superman. Lukes best moment in the OT is when he faces Darth Vader prematurely and losses his hand. But obviously it doesn't stop him and merely sets up another shounen power upgrade session. Which is fine, but ultimately less compelling than the character shift of Han or Darth Vader.
If you were going to bring a character like Luke Skywalker back, and not do the same shit as you did with your typical mentor-for-the-hero characters, I think what they did with Luke in TLJ was super cool. It has more of a significance because Luke is like Space Jesus. He is the hero of heroes for boys and men. An all powerful bad ass. Super cool. When I was a kid I loved Luke the most and identified with him. When I grew up I realized he wasn't very multilayered. And that is okay. I was just happy they made him more interesting in the TLJ than he had ever been before.
It comes down to having seen that sort of infallible heroic good type of hero so many times. So many video games where the player character is a similar save-the-universe-type of character, explained by tropes. Rian Johnson felt SW was treading the same ground, so he took it a different direction. Shame about the prison planet, shame about the fluff plot and characters like Phasma. Shame about all the cute critters who are there to primarily sell toys. But I am fine with all of that. I loved Yoda and Luke in this film.
