Elneny did not pay off for him when he made that decision to play him so . I wholeheartedly agree though, it is irrelevant because we don't make those decisions.When Wenger was secure in his position as manager, he played the young players because win or lose, he would still be manager following season. In addition, in those early days, big teams didn't play majority of their first team players in cup games (at least not until you got to the final). These days, teams like City have third teams that would dismantle many top premier league sides.
In Arsène's final days, especially when fans became disgruntled, opportunities for young players reduced. The current manager does not have the luxury of a secure job or fans patience that Arsène enjoyed for many years. He needs to play players he 'believes' will deliver for him. What you and I think in that regard, is irrelevant. Doesn't mean we are wrong, but just means when Emery watches Elneny and Willock in training, he believes Elneny will do a better job in a real match situation. He is paid millions of pounds to make those decisions.
I would love to see our young 'uns in the first team especially Bukayo or Willock. But I am willing to wait till the manager thinks they are ready. This could be next match, next month or next season.
Regarding being willing to wait, I don't think being willing comes into it - we have to deal because it's not our decision. I just think it's a bad decision to ignore the youngsters personally because we will lose them and regret it IMO, but the game is the game.