To be fair to Ten Hag, even after Frenkie de Jong left Ajax, they still played the same possession style and dominated the Eredivisie. He just shifted from relying on de Jong's unique talent for dribbling out of pressure to relying on Martinez, Timber and Blind to pass their way out of it. But there was a video posted here in the summer after Arsenal singed Jurrien Timber showing how good he was at playing out from the back and some of the passes that Martinez, the Ajax goalkeeper (Passveer?) and Timber were playing just seemed ludicrously risky even in that.
It just seems to me that Ten Hag's football, while being incredibly easy on the eye when it works, relies on his players taking massive risks both in and out of possession. Like we scored 12 goals in the Champions League group stage this year in a group which had Galatasaray and Copenhagen and finished bottom. In fact, we scored 9 in the 4 games against Galatasaray and Copenhagen and got 4 points out of it. Even Ten Hag's Ajax, who were a brilliant side had defensive issues in the Champions League. There's the aforementioned 3-3 draw against Bayern in 2018/19. There's also a 4-4 against Lampard's Chelsea in 2019/20 which Ajax led 4-0 after the hour mark. His style is an incredible amount of fun, but is also basically an insane high wire act to pull off. Which is okay if you have the best players in the league like Ajax had in the Netherlands, but the risk-reward ratio doesn't always work out in the Premier League or in the Champions League where the teams have players who can punish you for mistakes.
Maybe if we just splurge the cash and get a Theo Hernandez/Todibo/Branthwaite/Dalot back 4 with Amadou Onana shielding them, the risk-reward ratio will work out and United will be this amazing team to watch but it seems like a leap of faith to me. It's for Ineos to decide if they want to take that leap. To me, it seems easier to get a manager with a safer, more reliable style and build around that.