I don’t know; there may be the case that it’s not the most ethical choice to move to an area where they are improving their personal QoL while contributing to the lowering QoL of the current residents. I think the ideal solution would be to attack those root problems until that moral dilemma subsides somewhat. What I don’t think is probably the best choice is to blindly do what’s best for oneself while being oblivious to the systemic effects. I imagine there is a reasonable middle, like moving but consciously deciding to only support local businesses rather than buying from the cheaper MegaCorp, supporting policies like high density housing that may not be in your personal best interest, or dedicating a portion of your relatively high income to causes that specifically lessen those systemic effects.
Edit: as an example, I used to live in an area that was relatively poor by US standards. There was a large cohort of retirees who would move in because if the pleasant weather, low cost of living etc. Rather than mingle with the locals, they tended to create little walled enclaves. Additionally, they gradually took over the local government (in part, because the full time political positions were unpaid, meaning only those retired or wealthy enough to not work could afford to fill them). This created an environment where business investment was often stifled because the retirees didn’t want to lose the feel of their retirement settlement by allowing more homes to be built or certain businesses to open. It was difficult to raise any taxes related to investing in schools or infrastructure because retirees tend to be more price sensitive in those areas, particularly if they don’t have children or grandchildren who will benefit. Ultimately, this made it harder for locals to find work (outside of service jobs) or to keep younger locals from fleeing for better prospects. To many locals, it was viewed as almost a hostile takeover of their town by outsiders with money. It tended to exacerbate rather than alleviate those class divisions alluded to in my original comment.