Killmonger wants to change the Status Quo, and part of his motivation for this was a bad thing that our protagonists country/ancestors did that contributed to the villain's tragic backstory.
Then the protagonist literally goes to his ancestors who ruled the country and did the bad thing that enforced the status quo that motivated the villain and said "You are wrong, you are all wrong to turn your backs on the rest of the world" and then it ends with him fixing the problems that the villain was complaining about, just not via ethnic war.
Incredible how bluntly movies will say "the message is that we should solve these problems peacefully rather than through murder :)" and people will choose to pretend it says "the message is that we should never solve these problems and anyone who tries must be murdered" because it's easier to have a hot take about.
It's like, basic 102 writing, the second you graduate from baby stories for babies, you think "what if the villain had a sympathetic motivation" "What if he did bad things, but wanted good outcomes, but was wrong about how to do them" "What if the hero therefore had a more complicated feeling about them than just plain hatred". You know, the narrative techniques you graduate to when you're not a young child, the earliest and simplest forms of nuance.
But for that people even that escapes them, they haven't progressed past morality tales for children and naked propaganda, and if it doesn't compute as naked propaganda for their beliefs then they have to assume it's naked propaganda against their beliefs.