I don't think there's much of a mystery here:
1) Going into the season, we vastly overrated the O-line. Wynn is fragile and soft. We are having to play a number of linemen who shouldn't even be on the roster. The coaching is obviously sub-par. See if a couple million will get us Scar back, I guess.
2) The running backs need to hold on to the ball. We may have turned a corner on this, and overall the rb's remain the potential area of strength we thought they might be going in.
3) Bill Belichick is a sub-par GM, it is painfully obvious at this point. He blows at drafting skill players, and the shopping basket of players bought in this year's buying spree - AS IN PREVIOUS YEARS - is meh, at best. The Krafts should force a change here, get a competent GM on the job, ideally not one of Bill's sons.
4) Mac Jones is fine. He is often their best offensive player. The Wiggies of this world have their heads you-know-where. Mac is good enough, and the situation is dire enough, that Josh needs to let him off the leash.
5) The defense is abysmally coached. They can't even get the requisite number of players on the field. Their adjustments are all over the place. The defense is so complicated - and the coaches and players are so confused half the time - that they always fail in the critical moments. The Mayo/Little Stevie thing is not working. I suspect neither of them is really up to the job and that their "collaboration" just leaves both of them lost. Get a professional in there, and simply the d----d defense so the players can play. The only good thing about the defense is the game-to-game strategizing, and that is Bill's work: not Mayo, not Steve.
6) Overall, his team simply does not have enough talent to succeed. Get a GM and fix this.