The title's pretty condescending. I can understand complaining about other poster complaining but telling them to grow up because you don't like what they're saying is a lesson you should apply to yourself.
Personally, my issue with the team has been the lack of focus and intelligent play. Too much sloppy, careless, lackadaisical play pure and simple. Bringing in veterans over youth is supposed to avoid exactly those types of issues. To me, that's worth complaining about because it's something well within the players' ability to address. Granted, that's not the bulk of the recent complaints.
The team's not too old or lacking talent. This team, from purely a talent standpoint, is the cream of the crop in the league. However, their recent efforts in games is sorely lacking.