Stormtroopers don’t get old very often. The few that do probably get a nice retirement package. 😉
What happened to his son was obviously painful to Han. Remaining with Leia and the Rebellion/Resistance would only remind him of that. I doubt being a war hero leads to lucrative product endorsement deals in the SW universe.
And I disagree that Han has not evolved. He cared enough to get back involved in the fight, take Rey under his wing, and risk his own life to try to save his son. That it cost him his life is beside the point. The old Han would never have walked out onto that bridge.
Why would we get all the answers to the mystery about Rey, when there are two more movies to explore that in?