Van der Vaart has also taken aim at Ten Hag for his bias toward his former players and countrymen and warned him he desperately needs win to avoid the sack.
Since taking charge at Old Trafford in April 2022, the under-fire manager has spent over £600million on 21 new arrivals despite a large number flattering to deceive.
Compatriots Tyrell Malacia, Wout Weghorst, Joshua Zirkzee and De Ligt all joined under Ten Hag while five players he coached at Ajax - Andre Onana, Noussair Mazraoui, Lisandro Martinez, Antony and De Ligt again - were also snapped up.
De Ligt was recruited from Bayern Munich alongside Mazraoui in a double deal and Mail Sport understands around £38.5million was splashed out on the centre back.
Matthijs de Ligt makes 'too many mistakes' and is a 'little bit too wild', the pundit believes
But Van der Vaart, 41, has hit out at the muddled strategy and believes it has only heightened the pressure on Ten Hag after a sluggish start to the season.
'Yes, it's tough, I think, he's been there a few years and really spent a lot of money for his own players, which I don't really like,' Van der Vaart told The Sun.
'When you as a coach, you bring a lot of Dutch people in or players, I am not the biggest fan of that because when you lose a few times then the pressure is even higher, and the football is also not really getting better.
'I saw them against Liverpool. Of course, it's a tough pill to swallow because it's like the biggest game - like the North London Derby - and you lose without a chance.
'Now he needs a lot of wins. Then he will survive but we will have to wait and see.'
Van der Vaart also voiced his concern with De Ligt, sharing his disappointment with the centre back's performances and lack of development.
Asked whether De Ligt is the answer to United's defensive issues under Ten Hag, the pundit replied: 'A few years ago I would say 100 per cent.
'But when he left Ajax, I have to say, I'm a little bit disappointed in his development.
'So I think he is quality. He's fantastic. He's a great guy. Works hard for your team, the best, top player but he makes too many mistakes. You also need a little bit of luck, and he is in the phase now that he's really unlucky. And then he's a little bit wild.
'He was a little bit too wild [at Ajax]. So that means, going into tackles. And you think, "Hey, stay relaxed. Just look how the situation ends."
'And he went to Italy. Then I found out there he's gonna learn how to defend. But I'm not happy with what I see.'