Detroit construction and manufacturing licensing / ordinance laws are written specifically to protect existing businesses from new competition !
That's how most licensing laws work for commercial ventures. It's ridiculous. There are some narrow areas where there's a benefit to licensing restrictions, but they are badly outnumbered by cases where they do nothing but protect incumbents. Construction and manufacturing are both particularly bad in this area. I had a look at the site you linked to, and getting a business license in general doesn't seem so difficult, though I doubt it's as easy as they make it sound. What sorts of walls were you hitting?
All that said, Detroit's cesspit status has vastly more factors behind it than restrictive licensing for new construction manufacturing businesses.