Coach Erik Ten Hag knows when to include certain players in a match, because the coach also has his own strategy for it, even though the spectators or fans outside the field see it as wrong, even though according to the coach it is the best. Because when an injury occurs, a player will not recover in one day.
So the coach must really know about it so as not to misapply his strategy every time there is a match.
Ten Hag is like David Moyes and Pochettino but he has achieved more success than Moyes and Pochettino. Their common is they left Everton, Totteham and Ajax to take a higher challenge in their career. Moyes and Pochettino failed to satisfy command of their clubs (Manchester United and PSG). Ten Hag is facing with the same failure but it is only a few months for him in Old Trafford.
I believe he can do his job better. Give him time and come back in the end of this season to verify his work. Think of Mourinho, he started last season not too well with Roma but after the summer break, Roma came back and improved a lot. In the end, they won the Conference League.