While almost everything you said is true, it is rather hard to succeed in PSG midfield.It's not as clear cut. The main issue is Barcelona is harder to break through at than the likes of PSG playing in a one team league. If Arthur can play and impress everyone, starting very important games, then De Jong shouldn't have that many concerns, unless he's doubting himself. If he's got the goods he'll play everywhere, including at Barcelona.
Thing with Valverde is that he doesn't give too many free chances, that's wrong of him, but many managers are like that. But if you play and impress, chances are you'll play again and become a mainstay in the team. But De Jong doesn't seem too sure about himself and his abilities. And yes, in that case, he could be afraid he'll end up like Malcom.
De Jong is one of those guys that instead of rising up to the challenge, they prefer to lower the bar. It's not wrong in the end, but you'd have hoped for more from him considering the hype around this player. If he would've been this generational talent, he wouldn't be worried about possibly competing with Rabiot. Or ending up like Malcom.
Think about it. PSG could play a first 11 filled with squad players until the end of the season and still win the title in april. De Jong will receive more leeway for poor performances at PSG than he'd ever get at Barcelona, because nobody is anywhere near PSG in France.
At Barcelona pressure would be on him from the start. At PSG he can slowly progress without any pressure almost.
Cabaye was in France national team and highly rated in Premier League and couldn't make it. Krychowiak was in team of the year in La Liga and he was dropped after few games (he was boycotted by teammates because he was not at the technical level required, they would not pass him the ball).
This is somewhat a compliment to Rabiot, though, he certainly has the ability to play there (which explains the will of Barça board to take him).