1. No, it's not 50/50. Belichick is the best coach of all time and he can't turn an old team short on talent into a winner. Give him even the Browns and they're probably fighting for the division/conference lead.
2. The Browns ended up with busts every draft because they had a long string of bad GMs.
3. I'm not a huge fan of Arians personally but he's won everywhere he's gone. The only reason he was let go was Ben didn't like him.
4. Butler was a joke till Colbert rebuilt the secondary.
5. The Steelers' offense not being able to move the ball without Ben actually does more to prove the point that it's mostly talent that wins, not coaching
Rams fired Jeff Fisher, hired McVay and became a playoff team almost immediately.
Tampa had the worst D last season, this year it's top 10 under new DC Bowles.
Niners were great under Haurbaugh, awful under next HC, now great again under Shanahan. Coaching matters. A lot.
BB is a prime example. His teams always lacked talent, yet he found a way to win. Remmeber when Troy Brown, a WR, played DB against the best offense in history?
Talent is obviously important, but it'll get you nowhere without the right coaching.