Boogie's skills are undeniable but, as you point out, his intangibles are too. However its hard to assess an acquisition of Cousins in isolation - Ainge is clearly looking to do something else, along with this deal, such as Love, Pierce and/or Lopez. That makes the move a bit more interesting as Cousins D is a great compliment to Love's stretch four capabilities.
Furthermore, Boston isn't going to acquire much help in this year's draft and, more importantly they aren't getting a premium free agent until or unless they can get another piece in place. Cousins may not prove to be an attraction but he certainly is a start and most likely the best option for the C's to become relevant near-term.
Its all moot unless the picks are Brooklyn's though. Randive, despite the Simmons cartoons to the contrary ("Stauskas! Stauskas!...how about Stauskas!") is a smart dude and isn't going to give up Boogie unless he gets a haul in return. And yes, at this point I move the top picks to get DeMarcus Cousins but I am always biased in favor of realized potential versus that which could be great (but might not be).