You're entirely correct that most of the pure speed that we have wasn't being utilized in an ideal manner.
On offense, for example, how many times were we all hollering at the screen, yelling "STOP RUNNING THAT DELAYED HANDOFF 5 YARDS DEEP IN THE BACKFIELD!" and seeing our RB's come away with a 5 yard loss? The fact that we stuck with that silly delayed draw with the poorly performing offensive line in the earlier part of the season shows that someone was unwilling to use our talent in the best way possible. Even Rocket Ismail wouldn't have been able to get much out of those plays.
Brian Kelly has had a bad habit of trying to shape the players in his mold, instead of adapting to the talent we had. Seriously, trying to turn Dayne Crist into a spread-option / dink and dunk quarterback, instead of letting him be a downfield passer? Forcing Jaylon Smith to sit back in coverage and be a read and react player?
Those 8 win seasons in 2010 and 2014 could easily have been 10+ win seasons if he would have simply played to the strengths of his players instead of trying to force square pegs into round holes.