I think, SA needs keyattributes. F.E., if you have the penalty-king, you need shooting and/or finishing. The reason, I think so, is, I had a lot penaltyshootouts (many friendlies) at the last few days. I saw so many of them don't scoring... and after checking them, they are defenders with shooting/finishing around 1-20% or (D)Mx with finishing around 1-20%.
My penalty-kickers are the best on shooting/finishing. In my whole career my player only missed three penalties (1 missed, 2 saved).

The interesting part: my CK is better at crossing than my PM, but my PM is much better at creativity... so, maybe you need crossing and creativity for a good CK.