Did you think Ten Hag's poor season at Manchester United is because of a few players being out due to injury? Even if the injured players are fit to play, Manchester United will continue to perform as they did. Take a look at Liverpool, they are greater than Manchester United, yet they have more injured players. Liverpool has more players absent, but they are still winning games and competing for the title with Manchester City and Arsenal, can Manchester United do the same with the players available? Manchester United are still struggling to break into the top four.
We may blame Ten Hag's, he's in control and responsible for everything. The current squad cannot do anything for Manchester United, they must sign players during the transfer window. Consider Manchester United's defense line, Varane can no longer defend and there is no one to replace him at the moment. Even in their last game against Liverpool, Manchester United could not have equalized, if Klopp had not removed his top players.
The absence of players due to injury is still one of the options that Manchester United's performance is a little worse but in other respects as you said regardless of some players being injured or not it will not make Manchester United's situation better because after all their problems are more complex than that.
Indeed, the presence of players will provide a new spirit where Ten Hag can apply some schemes according to the will he wants but on the other hand, with Ten Hag's current way of coaching which is indeed more likely to prioritize ego rather than chemistry between each other it will still be very difficult to happen because it is an inability of Ten Hag to control the players especially with the current conditions, the chemistry of coaches and players is important but Ten Hag cannot do that just because he cannot control his ego.
As long as that is still going on, there is nothing that can be done apart from consistency that will never stabilize.