It's the players who are mostly responsible for the situation. Yes, management drafted them, but they simply don't play well. You look at a team like the Cowboys, and, collectively, their players are simply fundamentally and technically better than the Rams' players.
You watch a player like Sean Lee, a LB, and you see him make a leaping interception in the end zone where he catches the ball at its high point. The Rams' DBs can't even do that.
You watch a WR, Terrence Williams make a toe-tapping TD catch on a corner throw, and you think about Tavon Austin and how he needs to be "in space (read wide open)" for him to even have a chance to catch the ball in his tiny little hands.
You can always tell how good a team is by how much they get out of their high round (rounds 1-3) draft picks. The Rams don't do too well in that regard.