"There is a large area that is in very dire shape... but is no worse than it was 20 years ago"
This is absolutely untrue. I live in Detroit and work with its property data on a daily basis. The physical state of the city has deteriorated significantly since the financial crisis of 2008-9.
The downtown that is resurgent encompasses 7.2 of 139 square miles. Most of the city has not bottomed out. People continue to leave, properties continue to burn, and the news of Detroit's resurgence remains greatly overstated.
Take a look here to see how Detroit has fared since 2008: