I disagree

I think too often we're inclined to see the world as full of "questions" and "answers". "How good are the Rams?" "They are #10 on our power rankings, so they are the #10 best team in the league!"

Instead we should all be a little more Bayesian.

Ask questions of the world in the form of a hypothesis: "I think the Rams are good enough to make the playoffs," and adjust your hypothesis based on the available evidence. "Well, this site power ranks them here, this other site says this, PFF gave this grade but I think that's a little low based on this performance I saw from this player."

People think PFF is garbage because they think PFF claims to provide perfect quantification of football, which is ultimately impossible to perfectly quantify. I think if you asked anyone who works for PFF, they would say that's not at all what they are claiming to do.

They are simply providing one more lens through which to evaluate the game. That's it. It's up to you to interpret their work as you see fit, and combine it with evidence from other sources you enjoy reading to make up your own mind.

Personally, I appreciate their efforts, and am thankful that we have something other than the dribble from ESPN to help us understand our favorite sport a little better.