Wilshere, Welbeck, Ramsey and Ox have all suffered from injury problems. The latter two have come a long way from the players they were when they first arrived. Walcott was a one note player who only knew how to run in a straight line when he first arrived, but Wenger managed to turn him into a >10 goal a season winger. That is a good return for a player with such a limited all round game like Walcott, who can neither dribble or hold up play.
Gibbs was never that talented to begin with and is injur prone to boot, Wenger is good developer of talent but he can't turn water into wine.
He even managed to improve someone like Ozil, who hardly scored and was gassed in every game at the 70 minute mark. Now he's added goals to his game and his all around fitness has improved. He has to create chances for players like Giroud instead of Ronaldo so his assist ratio has gone down but I still think he's a better player than he was in his first season here.
I said Wenger develops young talent and improves their game but other factors will determine whether they fulfill their full potential.If Mbappe is going to become the best, he has to remain injury free, maintain the right attitude and work hard. Wenger will provide the best environment for him to do that. His tactics may be outdated and he's lost a step in the transfer market, but there is no one better out there at bringing up young players and giving them the opportunity to shine.