For one thing, I think any coordinator who has head coaching experience is automatically overqualified for the job.
Another thing, I heard this on Chuck and Chernoff, but Koetter's best year with Atlanta was '12, and one thing he did a lot of that the Falcons haven't done much of lately is throw to the backs. Turner, Jacquizz, and (lol) Snelling combined for over 100 receptions that year. Devonta's hands are fine, and I think that could make him even more of a weapon when he's healthy.
Last of all, Koetter and Kubiak have tons of NFL experience. Sark and Marquand were first time coordinators, I think just having some level of success at the NFL level for that long guarantees a degree of competency that I was never sure Sark had.
I was ready to run Quinn out of town at 1-7, but the team kept playing hard for him, and once McGary and Lindstrom came back, the O-line played a lot better. We even had a little bit of a pass rush there.
I'm sure the vultures will be circling quickly if they get off to any kind of a slow start next year.