I will offer this from an Indy perspective...
Fangio's defensive schemes were criticized by management and others (not too many players, though) for being TOO complicated to understand. Too many times, players were missing assignments and getting toasted.
BB's defense in New England is often referred to as the most complicated, but that is from the perspective of the offenses playing against them. It's actually a defense that his players understand well. Fangio's D scheme is difficult to play. It's also a downside for the Texans, b/c Manning knows what it looks like after practicing against it for so many years.
Jim Mora would possibly still be the head coach in Indy if he had fired Fangio, but he wouldn't, so he's now gone, too. I was sad to see the T's pick up Fangio, because I was worried about how a young team would pick up his D.
Man, I did all that talking just to say that firing Fangio won't solve all your problems, but there is more than one problem to solve, so it's a step in the right direction...