I'm a firm believer that the teams are made by their coaching staffs. Every team in the NFL has good talent. Sure, there's a difference, but the difference isn't as great as it seems to most people. Every year there are major turnarounds. Just look at the NFC South. One year the Carolina Panthers are in the Super Bowl and very close to winning it with NFL MVP Cam Newton. Another year the Atlanta Falcons are dominating the Patriots in the Super Bowl and if not for shifting away from their successful aggressive defense into a Prevent Defense that only prevents winning, Atlanta would have won a Super Bowl. The Tampa Bay Buccaneers have ebbed and flowed during that time tasting both success and failure. Now a resurgent defense has enabled Drew Brees to lead the New Orleans Saints to the best record in the NFL, home field advantage in the NFC Championship in the Super Dome, and possibly a Super Bowl.
And this year the former Super Bowl Atlanta Falcons were terrible, and the former Super Bowl Carolina Panthers were poor, and the Tampa Bay Buccaneers hit rock bottom and flushed their entire coaching staff. All of this from one division in just a few years. Most of those teams are still in tact. What truly made those teams rise from mediocrity to the doorstep of a Super Bowl ring, and back down into mediocrity? Not a lot.
So, I'm of the mind that coaching wins. Don Shula hemorrhaged coaches and coordinators every year, yet he kept winning games and divisions and kept competing for greatness. Today Bill Belichick is doing that as well. Look at the 4 teams left in the playoffs. Each has a top coach and a top QB. The coaches may be the best 4 coaches in the NFL--Bill Belichick, Sean Payton, Andy Reid, and Sean McVay the up-and-coming wunder-kind. The QB's are pretty good too, Tom Brady, Drew Brees, MVP candidate Pat Mahomes, and former 1st overall pick in the entire draft Jared Goff.
So yeah, without a top coach, we're not winning. But Sean McVay flipped the script in one year. IMHO, if you can find the next great coach, you can do it. But a mediocre coach like Sparano isn't likely to do it, and even if he does, he can't sustain it.
IMHO, none of our remaining head coaching candidates are good enough to do it. Fortunately, our best strategy is to suck for a year and get a good young QB in the 2020 draft, and that looks to be what we're going to do. But … don't be surprised if some journeyman QB engineers a late-season run to deprive us of a top pick, kinda like what happened just before the Andrew Luck draft.