How so? What did CAPE say would happen in 2014 or 2015 or for that matter last year? Or more importantly, this year? 

CAPE provides, from what I've seen, a very general long-term perspective on market valuation (are we currently, likely undervalued or overvalued based on historical data, ignoring interest rates and based on this static formula, are we likey to experience above average or below average returns over the next decade?) It tells us nothing about what we are likely to experience over any timeframe that is less than CAPE's decade-long configuration.
Is CAPE useful? Sure as general background information if you want to know if the market is currently cheap or expensive.   Should anyone use it to make investment decisions today?  Doubtful.