That doesn't really prove he would be better than those he's in the team ahead of though, Sterling has been pretty terrible outside the 2 goal contributions, and is a key reason why England look so lacking in creativity. Sterling is in the team ahead of players with a lot of goals to their name, so there's no reason to think those players wouldn't be scoring, and the team might look better for it. Sterling being wasteful also always becomes all the more apparent against better teams where chances are more limited.
The inverse of this theory would be to say Mings should keep his place ahead of Maguire, and some were saying this, but it's nonsense really. We need to find the best team, and it's quite apparent this team is not performing.
As an aside, England still would have qualified with 3 0-0 draws anyway, so it's not strictly true to say Sterling's goals are the only reason they aren't out, Portugal qualified with 3 draws last Euros, and 3 draws would already be enough here, yes the format is that bad.