They need to buy players, but they also need to sell players. The squad needs a complete overhaul. And if that happens, it's difficult to see them all gelling as a team immediately. It will probably take quite some time, and Man U might have to get used to being outside the Champions League places next season, too. The big question at the moment I suppose is how much of a draw are they to prospective incoming signings? Would the world's best players want to join a team that's not playing CL?
Yes, there must be an overhaul in the Man United squad, so the burden that must be carried by Ten Hag is quite large because no one knows how long he will be given time to fix Man United. Therefore, Ten Hag must take action as quickly as possible and the top priority should be fixing Man United's defense and maybe looking for a defensive midfielder who could play the water carrier role.
With the current conditions, it might be difficult for Man United to get world-class players. It's not just because they don't play in Champion League but it could be due to limited funds, so there really have to be some players to sell.
A total overhaul should have been carried out by Ten Hag right now at Manchester United, I think you will also agree if the current Manchester squad is not qualified to be maintained until next season, I think only 30% of players who are worthy of Ten Hag are kept to fill the line-up of him choice next season, while the rest might be better for Manchester to sell these players and use the sales money to find the ideal player so that it fits the criteria that Ten Hag wants, just like you, I also hope that Manchester defense should be the main focus Ten Hag and I think apart from Varane, none of the manchester united defenders are worthy of being defended at this time