He wasn't really tried at Schalke nor was he the player then that he is now.
Being one footed didn't stop a trailer load of good strikers including the greatest Messi. So that's not an issue that can't be overcome.
He was not only younger then but as he matures and fully develops it's a position he has more tools for than most current strikers do.
He already has free-kicks, a thundering shot, Pace and Athletism and a decent sense of timing, supreme confidence and calmness in the box. Just add penalties and an improvement in the air and he is easily a 25 goalscoring striker a season.
He wasn't really tried at Schalke
You lose all credibility when you bring up Messi as a comparison because his right foot is better than 99% of professional players and he has *literally* hundreds of goals and assists with his right to prove it.