Prime Iniesta would stand out in a way in which De Jong just can't. The difference in quality is too big imo. But then Iniesta isn't just world-class. Iniesta is a tier above, so when you refer to world-class players don't pick Iniesta, Xavi, Zidane etc. These are higher level than "just" world class.
Someone like De Bruyne for example would look fairly average at this Barca. So would any of Madrid's midfielders, and even someone like Verratti. In fact, from the current crop of top midfielders, don't think there's one that would be able to elevate the overall output of this Barca by much. We simply miss too many pieces atm, so it's basically a bottleneck effect, where the team would just capitulate at 3-4 positions occupied by really washed-up players.
You need 4 transfers that will work very well before you can really hold players like De Jong responsible for his performances. Ferran Torres is gonna be one, chances are good if he comes. Cavani probably 2. You need one fast winger as well. That's 3. Plus a top CB. 4 players to change the face of the team.
How are we gonna sign these 4 without selling De Jong
... no clue.