Almost certainly horseshit given the source but out of curiosity, in a hypothetical world where he was available how would De Jong fit into our midfield? Obviously he'd be a massive upgrade in terms of quality but I haven't seen as much of him in recent years so haven't followed the type of player he's developing into.
He is being used outside of his strengths at Barcelona, which can be explained by the presence of Busquets. He is mainly being used higher up the field, therefore not being heavily involved/the go to guy in build up of the play from the back. Where he plays now at Barca you would expect another type of player who is more involved in the final part of the attack and brings goals/assists. He is just not that type of player, never been. He gets criticized a fair share in The Netherlands by certain people that he lacks goals and assists. For me personally thats a load of crap. It would be the same as if we would expect Pirlo/Jorginho/Verrati types of players to provide threat in the opponents box in stead of judging them on their playmaking capabilites from behind the ball.
That being said I honestly think he should leave Barcelona. Barcelona will want to build their new team around Pedri/Gavi/Nico in midfield (which makes sense to me) and Busquets is also still there. Adding Frenkie de Jong to that mix doesnt make a good midfield, because it will mean more of the same players which will eventually result in (as you have seem happening now) one of more of those playing outside position and being used outside of their strenghts. Koeman has used him everywhere in the last year. Wide on the left, wide on the right, as central defender and as #10, but hardly as playmaking #6, because Busquets is always there...
He would be the biggest added value for teams who dont have a playmaking #6 at the moment. That basically leaves out PSG and Chelsea where Verrati and Jorginho are now, but I think every other top team can use him because they either dont have a playmaking #6 or he is better then the one who is there.. (Rodri at City for example).
His greatest strenght is that he is so insanely press resilient and has the ability to find space when the opponents presses hard (that is why it was so infuriating for me to see when they got slaughtered by Bayern earlier this season that he was playing soo high up the field he wasnt even involved in build up and the ball hardly reached him because of the Bayern press).
Would absolute love to see him at Real Madrid besides Casemiro slowly finding another long term solution for days after the Modric/Kroos tandem.
Have to add by the way: You can turn every stone on the earth and will fail to find a bigger Frenkie fan than me. But even i have to say he is massively underperforming and possibly in the worst form of his life these days.. Even playing outside of his bigger strenghts, I always expect him to do the simple things right and he isnt always delivering that at the moment.