A radical idea would be just to set play familiarity to 100 or 0 for all players on all teams and see if there is actual parity. We all know that offenses gain play knowledge (both individually and as a team) a LOT faster than defenses gain play knowledge (7 seasons running basically the same defensive plays? you get 50% play knowledge as a team).
But I don't think play knowledge is the real problem here. For me the problem has been, why is there so much open field? And why are LBs so non-existent in the game now? I looked at the stats from the first 5 or so seasons of MFN-1 and LBs were getting 100-150 tackles a year. Now a good LB may get 100 if he's REALLY lucky. And the "best" LBs in the league are going to average 60 or so. What I've been seeing is that LBs are getting sucked up into the block more than the OL is coming to the second level to make the block. ILBs should be playing 5 or so yards off the LOS, move laterally until the RB cuts, and then pursue to the hit. ILBs in the game are playing 2-3 yards off the LOS most of the time, especially if they are in M2M and immediately taking pursuit angles to the RB and getting eaten up in blocks. Or getting caught in situations where the OL is already blocking one player and ends up "blocking" two or three as the LBs all converge on the same spot. The WLB is the only LB that plays close to his talent level because, I'm almost certain, he plays in space most of the time and doesn't get sucked into blocks because there is not a blocker near. WLB is the only position worth having an LB above 70 overall unless you are going to treat your MLB as an extra DB in the nickle defense.
Since zone coverage has been really terrible for so long, most people resort to playing a lot of M2M unless you just want to get run over. So I see the issue as compounding. Not enough good defensive plays, bad player alignment, not enough lateral movement, players getting sucked into blocks, and finally (my favorite rant) poor tackling. I think that physical weight + speed + strength all need to be added to tackling skills. It's obnoxious to watch 190-215# RBs ping pong off of 240-260 pound LBs that hit them at full speed. The only way I've found to counter this at all is to only look at LBs that have 90+ tackling.
In short, if LBs played better, running stats would probably be more realistic. Right now, if the safety doesn't get the RB, he's gone.