​Why did Luke leave? Rewriting TLJ

While exploring fan theories for an Ep 8-9 rewrite that treats TFA as the baseline, I came across a proposal suggested by another fan regarding Luke’s exile: "Disagreement with the direction of the New Republic."

The post didn’t deep-dive into the specifics, which left me reflecting on what the "lowest common denominator" (the most universally accepted idea) might be among all the various possibilities people imagine.

So, I’d love to hear your thoughts on these two questions:

1. Why exactly did Luke feel the need to distance himself from the galaxy? (What kind of disagreement or realization would drive him to that point?)

2. Was his choice inherently wrong? In other words, should his arc inevitably lead to him deciding that he must return to the fray, or is there a valid reason for him to stay out of it?

How do you envision this?