IMO weak foot has never been weak enough on next gen versions of Fifa, it's most noticeable when crossing, Chris Brunt for example even has the "no weak foot trait" yet I can hit perfect first time crosses with his right foot, which is one of the hardest things for any player to do, look at all the problems England have had over the years with having to have right footed players playing LM.
A player with very poor weak foot, or especially with the "no weak foot" trait, should almost never be able to hit perfect, first time crosses with his weak foot, he should miss the ball and fall over most of the time with the crowd jeering at him