"That improvement is unfair to the people who ran it down"

Assumption 1: The residents are the people who ran down the neighborhood.

Assumption 2: Gentrification improves the neighborhood.

My previous comment addresses the first assumption. Feel free to disagree.

If a neighborhood is just real estate, assumption two is valid. If a neighborhood is a community of people, and gentrification moves a lot of the people, you have not improved the neighborhood, you displaced it.

Once we question these assumptions, perhaps we can address the root problems.