There are lots of rookie WRs who don't contribute in year one but turn into decent receivers. Of course, if GMs are as impatient as the OP, then probably not.
But guys like Eric Decker (6 catches), Cecil Shorts (2), Mario Manningham (4), Pierre Garcon (4), and Steve Smith with the Giants (8) all had quiet rookie seasons yet turned into pretty good NFL receivers. Don't forget our very own David Givens (9) and Troy Brown (2) in that group either.
I also think people have to factor in that we are always playing for a championship; we're never re-building. Rookies earn their playing time. I have no doubt some of our draft picks would have been better if we gave them a starter job and let them develop, but we can't afford to do that. They beat out a veteran or they don't get those reps. It's not about building up a few key rookies for the future; they have to learn to contribute to a winning team or they don't play.
If we were the Jaguars, we could play Boyce all the time and hope he develops quicker with experience. If we were the Raiders, we could afford to take a season off and give the kids a chance to grow and mature on the job. But we're in the battle for the #2 seed right now. If a rookie can contribute more than a veteran, great. If not, they sit. And I'm okay with that.
It doesn't mean that rookie sucks. It doesn't mean they're a disappointment (and not sure how 4th-rounders not becoming stars is a disappointment). But I always think of Bill Belichick's comments about how Tom Brady was a wasted roster spot in his rookie season. Just because you don't contribute right away doesn't mean you can't be a key contributor some day.