Basically, sometimes the value of draft picks is overvalued and sometimes they're undervalued.
I can think of 3 different examples where draft picks weren't valued, and all led to failure. Commanders, Raiders, and ourselves.
Couple of things you have to consider when giving up draft picks for players:
1) System. Many times a player is great in a system, but not so great in a different system. Joey Porter. Brandon Carr.
2) Age. By the time you are getting a player in a trade, they are generally around 28 or so. And many players are done around 29-30. For every guy that plays til he's 36 there are dozens who don't.