Considering Ramsey had a stellar game recently and was graded something like 55ish, I'm still taking PFF with a shaker full of salt.
That said, they are doing much better with their analytics as opposed to their data acquisition.
The problem I have is that bad data integrity means even worse analytics. GIGO
They've improved the acquisition from the early days when they had guys volunteering to do input, but unless they're going to the All 22 AND understand the calls by the offense or defense enough to KNOW each player's responsibility, then it's next to worthless.
Problem is that they're close enough often enough that people put stock in it... plus our on biases make these abstract numbers conversation starters... plus, people love rating/ranking things. It's literally part of our DNA.