His consistent lack of playoff success.
If by "lack of playoff success", you mean he hasn't won multiple Super Bowls, I guess that's true. But if that's the bar, there are a lot of garbage quarterbacks out there. He's played in five NFC Championship games, that's one step from the Super Bowl. And honestly, most of those teams didn't really have any business getting there. Packer defenses have given up an average of more than 35 points in all of their playoff losses with Rodgers. If that were true of Brady, there's no way he would have seven rings.
I do agree talk of Rodgers being the GOAT is silly. Honestly, you don't hear that being said much anymore, and I thought it was ridiculous to begin with. People said that more early on in his career, before Brady went on his tear. You can't really rip on Rodgers stats while celebrating Brady's. Rodgers' big claim to fame is his passer rating being #1 all time, largely because he throws so few interceptions. He takes care of the ball. I don't think he's a bad leader, but at the same time I don't think leadership is his strong suit. He's more of a lead by example and work ethic type of guy, rather than someone who inspires.
And Russell Wilson is pretty damn good. I say that, and I hate the Seahawks.