People want sacks. People want six tackles a game. People have unreal expectations.
I'm not sure how much you know about 3-4 linemen, but their job is not glamorous. It isn't supposed to be. Their primary job is to eat blockers and plug rushing lanes so those behind them, i.e. the linebackers, can make the plays. If they happen upon a blown assignment and make a nice play in the backfield, great. Kudos for them. But it's a bonus of the job.
Marcus Spears earned his starting job because he's good. He's damn good. And it would be impossible to find a rookie 3-4 end who did better (ever) than Spears did last year. Ever. I mean that.
And how in the hell is he injury prone if he makes it through a 16 game season without so much as a hangnail? If somebody rolls up on you or you step on somebody, there isn't a whole lot you can do.
Most people who know draft picks thought Spears and Ware could have been swapped. The fact that we took him at #20 was an absolute steal. I'm sorry if you can't see that, but I think you're looking in the wrong places.