Actually, Shanny's personnel decisions were worse (Niko Koutovides, Marlon McCree, Engleberger from Bad News Bears, etc...), and what ultimately got him fired was not punting the ball against Buffalo with 2:00 left in Week 16 of the 08 season. If he punts, they probably make the playoffs, and he would have been spared no matter how badly Peyton and co. beat them (which probably would have been 60-0. Denver's D was terrible, and they had a lot of injuries).
What you said about Elway, though, is pretty good. If he left, and Ellis was gone, this team would lose a big time cancer. I don't know what the great Pat Bowlen was thinking. He should have been looking for a new buyer around 2008 when he was going downhill. I don't know how he could even think about any of his family running it.