You may be letting your bias cloud this and severely overstating Shanny's demise. He's had interviews with half of the teams with openings, so to call him irrelevant is just inaccurate. He had some early success with RGIII, but was dealing with a diva QB, and a diva owner, and an ineffective GM who just got replaced. Granted he has some blame there too - but I don't think think the game totally passed him by as some have implied.
I think he is still a Top 10 offensive play caller. He is a Top 15 (above average) NFL head coach. I mean, look at some of the guys who are getting head coaching jobs nowadays. Dennis Allen? You want Jay Gruden over Shanny? How about Tony Sparano? There are plenty of talented up and comers too, so it's not like I'm saying I'd go out and hire Shanny for sure, but he's a legit and viable candidate for some of these franchises that need some veteran leadership.