Not to be pedantic, but that's not the point you tried to make. You implied they had too quick a trigger finger on firing coaches. The simple matter is that they allow the actual FO to handle it and step in when it gets too much, such as in the case of Millen (9 years) or even Mayhew (7 years). They are notorious for being hands off on daily matters.No one. For whatever reason they just have not been good at identifying coaches. Lions coaches are like Browns QBs. However, Its still way too much turnover. As you said it could just be that everyone just flat out sucks and its just been a massive string of bad luck. Its a combination of both there. I'm sure the coaches are at least consulted on possible draft choices so both share the fault. Perception is everything and ownership can be viewed as a negative for things like that.
One could certainly make the argument that they make bad choices in front office hirings, or stuck with them too long, but citing them for the coaching turnover - when everything we have speaks to the contrary, that they don't get involved with it - seems odd and inaccurate.