I hear you, but I think as fans of a team, we sometimes have an inflated or deflated sense of a player's worth. Perhaps I'm overrating Stevie in the same way I believe you are underrating him, as I'm a huge fan of his and I actually love his personality. I also think he's an excellent player. The problem is that, like I've stated earlier, his best attributes are not easily quantifiable. He's not exceptionally tall, strong, or fast. But his ability to create separation and get open is among the best in the league and unless a player is a total mismatch (which you can say for maybe 4 or 5 players in the league), that is the top attribute to have for a receiver, in my opinion.
People point out him throwing up his hands after that pass by Tuel, but fail to point out him running after the Colts DB and stripping him of the ball and recovering it late in the 4th quarter last year after yet another horrible Fitz pick. That doesn't fit the narrative of him coming up small in big moments, so its conveniently glossed over.
At the end of the day, a WR can't throw the ball to himself. His production is dependent on the QB and scheme. I don't think you'll find many people who would say Larry Fitzgerald isn't an elite receiver. But look at his stats over the last five years. He's had one year of 1400+ but the rest of the time, he's been just above or below 1000. And then look at his stats when Kurt Warner was his QB.
If you put Stevie Johnson on that Denver team in 2012 when Peyton Manning gets there, and Eric Decker was here, we're not having this conversation.