Because if used correctly, he is a forward who scores goals, can play in multiple areas and is an awesome defensive player to go with it.
If not used correctly, then like most players, not good things happen
England dont have better players than sancho. They just have a coach who doesnt know how to use him.
For his age, what he has already achieved is quite remarkable. Especially when you consider how rare it is for English players to leave England...it shows a huge mental strength and confidence...