So, you want to cut the character development out? That doesn’t make sense.
Luke is very clear about what he did and why, and SparkySywer did a great job summarising it.
Except that Luke’s reasons for exile are
1: He feels guilty about almost killing Ben/failing his new order
and/or
2: He thinks the Jedi are fundamentally flawed due to letting Palpatine rise under their noses and being vain about using the Force.
Both of these reasons amount to Luke ‘running away’ because in none of them does he draw a clear line between his power and the rise of the Dark Side.
As to this cutting out the character development, this is supposed to be Rey’s story in the first place and it merely streamlines the theme of Luke’s failure rather than complicating it with flashbacks and lengthy explanations that threaten to lose parts of the audience. If you need paragraphs to explain a secondary character’s motivations in a Star Wars movie, you’ve failed.