I don't think it's completely meaningless, it's a stat that tells you something so therefore it can be useful to a degree. That ideal is not analogous with a stat being an appropriate way of measuring a player. Like any stat, it usually is more useful with combination of more stats. I agree that it's not really that important, you can have the ability to hit a HR with more exit velocity than Giancarlo Stanton but if you are averaging .200 and K'ing 35% of the time who cares?
I think a more effective use of exit velocity would be to look at a players avg exit velocity on all balls hit in play. We all know a HR is going to be leaving the bat at a higher velocity but if a player is constantly hitting a ball with a harder exit velocity then it's because he is squaring up the ball more than other players. That's what it is telling you, just like HR's tells you how many time a guy hits a ball over a fence and BB% tells you how many times per 100 PA's a guy takes a walk. It's a stat, it tells us something. It might not be as useful as other stats but I don't think it is completely meaningless either.
Like I said before, it is "the new shiny toy" people are making it out to be a bigger deal than it is.