There are a few issues that are root causes.

Foremost of them, is we have a huge glut of people that skill wise, aren't worth anything to employers. I'm not saying they are worthless people at all, just that currently they don't know or can't do much that employers want to pay for.

Secondly, money is being syphoned from the city to the suburbs by city employers and suburban employees. There is little reason the infrastructure of the city should be failing with the huge amounts of money being generated inside city limits. I suspect much of this is from tax breaks for employers, and the terrible condition of nearby neighborhoods.

Third is the culture. Downtown Detroit is half urban city center, half broken down ghetto. There are very few nice places to live that draw money in. Near by, there is a ton of land occupied by substandard housing, employment, and infrastructure.

Honestly, the best route would be swapping the populations of the city and the suburbs. There's an ever expanding wave of the affluent trying to escape the city life and it's negatives while the ghetto continues to expand outward for the exact same reason. There needs to be a new wave of purchasing near downtown and building new homes on double lots (to lower population density) and increasing the police force to suburbanize the new developments. City property is shoukd be expensive, but it should also real the benefits of being expensive. Things need to be rebuilt from the ground up.