"it's not that simple"

There's no "that" for it to be either that simple or not that simple.

(Implicit modifier A) women (implicit modifier B) dig (whatever that means exactly) jerks (whatever that means exactly).

Modifier A can be "all", or "most", or "the most attractive ones", or whatever.

Modifier B can be "most days of the week", "most years of their lives", or whatever.

"Dig" can mean "prefer ceteris paribus", "will only have one night stands with", "will stay with them even if the guy hits them", "strongly prefer at all times", "prefer for all types of relationships", or whatever.

"Jerks" can mean "people who are more assertive than average", "people who try and make them feel bad about themselves", "people who have killed a man", "people who wear motorcycle jackets", "people who frequently brag", or whatever.

"Women dig jerks" provides an opportunity to construct an obviously (or not obviously) true or false meaning to something other people say, depending on how right or wrong one wants them to be. It allows room to always easily be able to interpret an interlocutor's words to mean that they are innately evil or hopelessly misguided.

That said, people actually do disagree on the substance of the issue.