Nothing wrong with your bike size, but most brands are shipping their bikes with shorter stems to make them more comfortable for inexperienced, aged, or unfit riders. If you've been riding a while and feel like you want a longer stem, you're probably right.

Trying to dial your reach by modeling your position after racers in postures of extreme aerodynamic distress is generally pointless. After dialing in your saddle height, saddle setback, and back angle, look at the angle from your back to the humerus (upper arm) with your elbows nearly straight and your hands on the hoods, where they will be most of the time. Something like this guy,

who demonstrates the position while showing that he is somewhat overextended. Look in a mirror, or have a friend measure. The angle should be about 90 degrees or a little less.

If you get a significantly longer stem to increase this angle, it might change your balance enough to require slightly increasing saddle setback.