It's not that they lost, it's that they were not competitive in those games. There's a simple blueprint for beating the Broncos--pressure and take away the middle, forcing sideline throws which require arm strength and the ability to step into a throw.
Some teams have the players to keep it up for 60 minutes--NE and STL obviously do. Raiders did so for longer than they should have--including two picks.
Problem for Denver is that 5/6 of remaining opponents have the defensive players to do what NE and STL did.
The trajectory reminds me of the 2012 NYG--QB and skill position players masked defects of a substandard o-line. Until they couldn't.
A team can have an iffy offensive line, or a weak running game, or a quarterback with mobility and arm strength issues and still win playoff games. It can't do so with all three.
Ironically, their defense is much better than the offense. Especially when they need to use third stringers at the skill positions due to injuries to RBs, J Thomas, and Sanders. Double team D Thomas and there's no one that can hurt you.