His entire speech to Laertes was clear and actionable advice. And his advice to Ophelia was likely necessary for the time. Had no clue people thought him a fool until today.
Shakespeare quotes should not be considered in isolation, they are always part of a larger context. Taking Polonious advice at face value is like the people taking the "greed is good" or "coffee is for losers" speeches at face value.
Because of the length of the play, the scene with the spy is often cut, since it doesn't directly concern Hamlet and doesn't really lead anywhere (we never hear from the spy again). But without this scene, Polonius advice to Laertes stands alone and is taken in earnest. The scene with the spy shows it is all dishonest bullshit which plays into the larger themes of the play, e.g. Polonius later using his daughter as bait and spying on Hamlet.
I don't buy the article author's contention that these are "dad jokes" or that Polonius is self-aware. He may be the best parent in the play (a low bar), but he's still a deliberately comic figure.
And nowadays I agree 100% with my dad - it’s great advice.