Come on, man. Payton and Arians can't complain about their offensive pieces. They've pretty much had them! No one is going to say with any type of credibility that they'd choose any offense we've had in the past five years over the Cards' or the Saints'. Cam ain't on Drew Brees' level yet. He's not, and may not ever get there.
One of the main reasons Reid hasn't gotten KC any further than they have is because they need an upgrade at receiver, just like we do. Hell, they are still looking. Now I will give you that if maybe Reid had Cam, then maybe he could do a little more.
I think one of the primary differences here is that, even at his best, Tolbert was fat, not very fast, and definitely not "quick".
McCaffrey is the opposite of all of these things.
And, as someone else pointed out, Tolbert was actually used a good bit and effectively when he first got here when he was still close to his "best".