In the time frame you are referencing, Kansas State, Maryland, Clemson, Bowling Green, and West Virginia were running this quirky offense that spread out 3-5 receivers and ran almost exclusively out of the shotgun with a blend of option and a passing game that relied a lot on play-action off of a shotgun-option look and even an occasional "sophisticated" play that involved a Q.B. option to run or pass.
Oklahoma and Purdue were running a pass-happy offense that was basically the run-and-shoot out of the shotgun.
Virtually everyone else who wasn't an academy was running out of 21 or 11 formations and taking most of their snaps from under center. A one-gap, four-D.L., blitz-heavy Cover 2 scheme can work well against those types of offenses. For the offenses listed above, such a defensive scheme is a terrible idea.
Every other program that matters has learned this and adapted accordingly now that the heavy majority of college teams run some variation of the spread.