Should Fleck re-evaluate? Yes. Certainly. Heck, I imagine he re-evaluates after every season, win or lose.
Should he consider changes on the staff, specifically on offense? Yep. Offense needs serious attention, especially the passing game.
Should Fleck, or any coach, alter his entire philosophy, developed over years coming up through the coaching ranks, because of one 5-7 season?
Hmmmmm...
Would you? If you started as a grad assistant, paid some dues, learned and absorbed as much as you could from experienced coaches, got one and then two head coaching opportunities and had some pretty decent successes at both stops...
... would you make dramatic changes to your hard-won, carefully-developed core coaching philosophy because of one 5-7 season?