We have to move past focusing on one part of the program. A football program has more than one piece.
First off, while our OFEI was great, what would it have been if you take away the BG and L'ville games (2 of the 8 worst ranked teams in F+ rankings in all of college football).
Despite having a Top 20 FEI, our overall F+ ranking was #76 - which was actually the worst of the Johnson's tenure (2017 - #67, 2016 #43, 2015 #61, previous worst 2010 - 74).
Statistically this team actually overperformed relative to its schedule and stats. It won 2 games against teams with a higher F+ (Miami and UVA) and only 1 loss to a team with a lower F+ (USF).
I enjoyed Johnson's time here - we were fortunate to have him for so long and get the highs he gave us (the avg tenure for college coaches is 3.8 yrs and before last season there were only 9 coaches who were at their current school at least 11 years - and only 2 over 13) - if you get a good decade from a coach like we did from Coach Johnson you are doing way better than you should expect.
https://www.businessinsider.com/college-football-players-coaches-recruiting-2017-12
But he decided to retire and frankly at times the last 2 years he has looked tired and just not as in to it as he used to - which is a big part of the reason I think he decided to stop.
I'd like to be good in all 3 phases of the game. With Gailey the offense was often painful but the defense was usually very good. With Johnson it was almost the opposite (it helped that Johnson was a better coordinator than anybody Gailey ever had on either side of the ball). But ultimately if you want to get better you have to become good in all phases.