At the end of the day Detroit is a city which was designed from the ground up to discourage public transport. Combine that with the lack of any sort of a population within walking distance of the Q Line and the line neither going or connecting to anything meaningful, the lack of expansion plans and at the end of the day you just have a shiny train to put in a press release that won't even see enough ridership to even come close to covering it's own cost.
Have a look at the cover photo in this article - Woodward is the centre right road in that image. https://www.nytimes.com/interactive/2014/12/07/opinion/sunda... - This is the road along which the Q Line is travelling. I think you can see exactly how much ridership one can reasonably expect.