I realize this is going to sound pretty milquetoast, but: I wouldn't use words like "worthless". Predicting the future is complicated and I think GMO understands the fundamentals and macroeconomics very well. They are directionally correct most of the time and for the right reasons, so I'll listen to what they have to say.

But I also don't think their predictions have sufficiently precise timing to beat the market. I agree with the thrust of your point, and I probably wouldn't invest my money with them. I think of GMO a lot like AQR in that sense.