Ross Barkley has a lot of potential, but his actual contribution is still fairly poor, which is fine for someone of his age but it wouldn't be nearly enough for a top 4 team, for example. Given that one saw discussion of moves to Man City and £50m transfer fees, I'd say his current ability is definitely overrated.
He scored 6 goals last season, which is good for a midfielder. But he had 0 assists. His passing stats are generally poor, he rarely creates chances and just doesn't make many passes in general, so it's not as if the former stat is restricted by his playing lots of passes further back or the possession based system he is in. His defensive contribution is also very poor, even taking into account his attacking nature. The areas he stands out in are dribbling and shooting, suggesting his style of play is to pick up the ball in midfield, dribble towards goal and have a shot. Which is fine, but the best attacking midfielders contribute all over the pitch.
Let's take Jonjo Shelvey as an example. He is a little older than Barkley, 2 years, but this was also his first full season in the PL, he is also english, similar style of player but one with considerably less hype. He also has 6 goals, but also has 6 assists, with decent defensive contribution and passing stats, as well as a similar number of shots. But you won't find Shelvey even in consideration for an England spot (interestingly, Shelvey also outmatches Wilshere in pretty much every area, and is the same age).