I myself, as a huge Messi fan relate to this somewhat. When I saw Messi play as a kid, I thought he was an anomaly. A superhero of sorts. It was too obvious he wasn’t like the other players. Just by looking at him, I knew instantly that what he was doing could not be learned or copied. One doesn’t simply try to walk through hordes of defenders without getting tackled.
This! and when we say this we don’t mean he didn’t work hard. If you saw Messi from the time he was a kid until now, you just immediately see that no matter how much you practised, no matter what you did, you will never be like him.
But if you have good size, good athleticism, you know that with hard work, you can somewhat be like Ronaldo
My guess is that Gnabry was still coming back from ACL and seriously lacking in self confidence in his game.