Compare the 92-95 Fins (Shula's last 4 yrs) with the 96-99 Fins (JJs 4 years). The 92-95 fins accomplished slightly more (2 division titles vs. 0 for JJ), had a better overall record (39-25 vs. 36-28), scored 2.9ppg more, allowed 0.6ppg more (simply better teams). JJ was a good talent evaluator (on defense) and an aggressive defensive coach. Horrid offensive talent evaluator and a very conservative offensive coach (Wanny-esque). JJ's 1000yd rusher was due to giving KAJ all the carries, despite averaging 3.5yds/carry (which is terrible). Shula's 94 team was a much better rushing team than anything in the JJ era.
JJ's offensive scheme was run the ball (which we never could do), then when you established the run (which we never did), run simple pass patterns that are open because LB/S's are playing the run (which lead to INTs, if the defense is not playing run). No scheming at all of offense, no audibles from Dan (!?), nothing. Simple, vanilla, easy to defend.
JJs defense was also overrated in Miami. Yeah, he got Zach/Taylor/Madison, but he gave up Cox/Coleman/Vincent (fairly even trade). Even in 99, Armstrong/Buckley/Bowens/Jackson (all Shula pickups) were significant contributors to the defense. The 62 (7-62) and 38 (3-38) points his defense gave up in the last playoff games of 98/99 make Shula's 22-37 loss at Buffalo in 95 look close. Plus, the allowed ppg were similar for these teams (19.6 vs. 20.2), with both defenses choking at a similar rate in the 4th quarter.
Plus, he basically scapegoated Marino for his own offensive personnel failures, which did not win him many supporters in Miami.