The team sucks, everyone agrees with that. But the coaching has sucked too, especially on the defensive side of the ball. The strength of their defense is their secondary so they to had force teams into passing and they just couldn't do it.
They rank 27th in run defense, 26th in rushing attempts against, and have the fewest number of pass attempts against which is not playing into their strength. It's up to the coaching staff to scheme up at least a moderately effective run defense that would drive up the pass attempts and create more opportunities for turnovers, etc. They are second in INT's but second to last in forced fumbles. They couldn't stop the run or create turnovers against the run. Abysmal failure by the coaching staff.
The offense is just a horrid mess of personnel. The OL is the only reasonably stacked position group (and free agency is probably going to change that for the worse). There's not much you can do with an offense that is dearth of talent at QB, WR and TE.
However, it's pretty inexcusable that Belichick has so stubbornly stuck with Newton, even with Newton clearly breaking down physically and mentally as a passing quarterback. Newton looked so incredibly inept on Monday night; he just cannot throw a football anymore. Literally cannot throw. And I know Stidham has played like hot garbage in limited opportunities but Belichick should have turned to Stidham full-time after he benched Newton in the Rams game. Stidham could have gotten first team reps and prepared as the starter. Then we could have gotten a more realistic look at Stidham in meaningful game action. By the time he entered the game Monday night, the rest of the team had already quit by halftime.
Newton is not a functional quarterback anymore. Stidham probably sucks but he at least looks to be functional and may have a sliver of hope to run an NFL offense whereas Newton should never take another snap.