Hue Jackson says
you don't defeat the other team you defeat the QB. And I think he is right.
Because the QB is the most important player on O that means on D your most important players are guys who defeat the QB. Or disrupt his play.
I think Jones is a fantastic player but you would have to offer me TWO of him to pry Donald away from me because Jones needs someone to get him the ball so his production is based on help from another player. Donald doesn't need anyone to produce at an amazing level he can do it alone.
Take Donald away from the Rams and the DL is still fantastic, and saying that doesn't reduce his value because he could go to a team with an average DL and immediately turn it into one of the most dangerous in the NFL.
Also with the rules being disadvantageous towards DB's the DL is the most critical part of a defense.