I think gameplanning is very important. But an average game planner with a top 5 GUESS team will almost always beat a great game planner that has a #20 GUESS ranked team.
A great game planner can beat a below average game planner if the discrepancy is more like #5 vs #12. But they normally still have to catch a few breaks (kick returns, turnovers etc).
There are always a few coaches in each world that light the world on fire with recruiting but perpetually fall in the 3rd round.
In my opinion, game planning is only important when teams are within, estimating here, 5 GUESS POINTS (not ranking) of each other. That's why I don't game plan for sims etc.