If you really believe the so-and-so is THE guy but that there's a very good likelihood he'll be there when your turn comes, why wouldn't you trade down? The only reason I can think of is the risk he's drafted before your turn is unacceptably high.
That said, getting more stuff strikes me as an "all else equal" argument. Lots of stuff isn't that helpful if the stuff doesn't include a "star" or if you don't already have that star on your roster (which the Jazz don't). Granted, you have to surround the star with quality talent to win, but quality talent without a star isn't likely to win.
I suppose one might argue for accumulating stuff now in the hope that a star comes down the road eventually. That makes a certain amount of sense. However, if you think your guy is a star, I don't think its worth the risk of missing out on him to accumulate more stuff if you think that risk is real.