Well, the inability to predict recessions, or the general moves of the economy for a start.

That seems a little shortsighted. Do you also think climatologists and meteorologists are charlatans because they can't predict hurricanes or blizzards more than weeks in advance?

You'll have to do better than that, because the majority of economic literature does not attempt to forecast movements, it attempts to model them and understand them. The "track record" you speak of is not actually the track record of economics, it's just a meme armchair economists like to repeat (generally without a non-snarky defense of their point).