If "people never change", you've now declared that Anakin's redemption was impossible, and that Luke could never become more than a whiny farmboy.
Clearly, that isn't even true of the OT, so it's bad form to attack the newer films for continuing with it. Ignoring the observable fact that the idea is incorrect, in terms of the real world; people change all the time. Not everyone, obviously, and some try and fail, but there are plenty of cases of criminals reforming themselves and doing good things, just for a really blatant example.
To make matters worse, the failure you see in Luke's flashback echoes his failures in the Original Trilogy. It's the exact same character flaws. So even here, this is a case where Luke didn't actually change. His apparent victory over the Dark Side at the end of RotJ was fleeting, and didn't result in lasting personal growth; he relapsed, briefly, in that moment.
Your argument here doesn't hold up for multiple reasons.
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See also "bad/shallow characters".
It's essentially an admission that you can't actually define what makes it "bad". You just don't like it.
For instance, to use a completely separate example we'll probably all agree on, take Avatar. I fuckin' hate that movie. Almost walked out of the theater. The reason I hate it is because the plot is implicitly racist as fuck. It's a "white saviour" story. The Na'vi are stupid aboriginals and are gonna get wrecked by the Awesome White Men, and their fates are sealed, until one of the White Men deigns to go native and out-natives the natives and saves them from the other White Men. Worse, the Na'vi are so lazily written to be Native American stereotypes (and the bad, racist ones at that) that it's just egregious.
Note that I'm using capitals because I'm talking about a long-standing trope. Making it about aliens and humans just means "White Men" are "any humans", even if the trope originally emerged in less-fantastic stories; it's not a criticism of white people or men, but a specific racist trope that describes aboriginals as "lesser" than the European colonists/explorers/etc.