Like if the O-line fails, he can't scramble like a Wilson, RG3, Krapernick, etc. to get out of trouble or run for a first down.
He's done that plenty of times. Like against the Panthers and got hurt. He'll never be like Robert Griffin III or those other QBs but so what...that's only 3 guys and 4 if you count Michael Vick. Tony Romo doesn't count. He's not a run first guy.
If the WR's don't get much separation, he isn't going to put it in the perfect spot like the elite QB's- and by this I mean when a WR is covered and he still throws it to him anyway because he can put it in a spot where only the WR can get it. He can do it occasionally but not like the elite QB's and I think he knows it which is why he tends to play it safe.
He's done that too. Like against the Panthers. Not his fault the ball gets dropped. Remember the Danny Amendola catch against Arizona last year? That's the example the is the most obvious to me.
He doesn't seem to make the best reads/adjustments at the line.
Well you don't know that, and neither do I. That is entirely subjective.
Manning and Brady are amazing at this.
Comparing any QB to Peyton "goddamn" Manning isn't really fair. There will never be a QB like him.
Tom Brady needs weapons too, and it's not his fault his production has fallen than when he had Deion Branch, Rob Gronkowski, Wes Welker, Randy Moss...
And second thing, your first point is that Sam "can't" scramble. But neither Peyton nor Tom Brady scramble like the guys you mentioned. They are the complete opposite. It's not needed.
That goes a long way in putting the other players in the best position to succeed. He never uses the pump fake or shoulder fake to draw defenders off his targets, either. That would help in bailing out a WR that has trouble getting separation. Stuff like that. Some may not agree but that's how I feel.
True, Sam might need to do those thing. The thing is tho...other players have to make plays too.