When you look at it, they have a massive amount of infrastructure for a huge city that lost of a lot of taxable individuals in a relatively quick timeframe. Unless they can move everyone to a more densely populated area of the city and shut down the infrastructure, they have to bear the cost of being a huge city without the tax base of a huge city. That's why tax is so expensive. Well, that and massive corruption.
I wonder if anyone in Detroit calculated pros and cons of "defragmentation": moving people to several designated areas and shutting down infrastructure in vacated blocks. I understand that US is not North Korea and it is easier said than done, but still would be an interesting calculation.
The people that have stuck around thus far tend to be really attached to their current location. If you get them to up and move, they might as easily move to another city (maybe where their kids are) then to the new district.
Which might still be worthwhile, or at least worth considering if things are truly as far gone as they appear from those blight maps. If the city is having to maintain water, power, sewer, etc. to an entire neighborhood for a couple of homes, having those people move to a different city and shutting the entire neighborhood down would probably save a bunch of money.