Michigan naturally has a huge vote sink area for Democrats in the Detroit metro....but the rest of the state doesn't vote heavily enough Republican to warrant all but 1 other seat outside Detroit being red. MI-7, MI-8, and MI-11 already are baconstrip districts almost really. That area in the southeast is probably what the GOP focused on the most in redistricting.
I do agree any sensible map would favor Republicans regardless of how it's drawn though.
There's only two other districts that are completely in Metro Detroit (which I consider the tri-county area). MI-09 (Levin) is blue, and MI-11 (Trott) which is largely middle and outer ring suburbs. MI-11 is grotesquely shaped due to MI-14.
MI-07 doesn't go to Metro Detroit at all and while it's a long and somewhat narrow area, it does for the most part keep county integrity which is important and traditional in Michigan. It's usually considered a Jackson based seat, if anything.
Most of MI-08 is outside of Metro Detroit outside of it's portion of North Oakland. I don't consider Livingston County metro Detroit, and Ingham County (one of the other main D bases) is definitely not Metro Detroit. MI-08/MI-11 could have been cleaner (they didn't want to bump Rogers and McCotter districts together and didn't want to create more county splits either)
Most of MI-10 is in Macomb, but it also has the thumb.
MI-12 is about 1/2 in the Detroit area (Downriver) and 1/2 in the Ann Arbor/Ypsilanti areas.