Ancelotti should have done it in the summer transfer window, but he said he would not recruit any more players. As the league started and at the same time the national team's international match schedule, Madrid experienced many players who were injured. Talking about defenders that Madrid had targeted or were linked, Magalhaes and TAA, were rumored to be recruited by El Real. But I'm not really sure if Arsenal will release this Brazilian defender, unless Madrid offers an attractive price for Arsenal. But it seems that if Madrid will recruit several players, especially defenders, there are actually still many options and they are also good. In fact, sometimes Madrid brings in players who were not expected before. Let's just wait for the next rumor, whether Madrid will indeed target new arrivals in January, or they will evaluate it at the end of the season.
The Real Madrid manager must have had his reasons for saying so. Real Madrid have skilled and experienced players in all positions but so far they have lacked a good man finisher which is where they pre-selected Mbappe even though they had to wait a long time to bring Mbappe to the club yet Real Madrid brought Mbappe to their club. Since Mbappe has come to Real Madrid, Real Madrid does not need any new players in any position, so naturally Real Madrid will not want to hire any other players in their club. However, if the matter is such that another club is offering a large sum of money to an existing player of Real Madrid, then Real Madrid can sell that player and employ a new player in that place.
The reason Ancelotti does that is because he believes in his players and while that's a good thing, it's also a risky choice, especially since he should have known that since he's been at Madrid for so long, he'd have to deal with the usual hurricane of injuries that happens every year, but Ancelotti pushes it too hard and thinks it's no big deal, which is a mistake that I keep repeating.
At the start of the season they lost a lot of players to injury and even for a long time which made their performance also lose a little momentum coupled with an incomplete attack line where Mbappe still could not give his best game added to Madrid's condition even worse.
Although now slowly Madrid are regaining their momentum but Madrid should know that now minimizing things like this is something that must be done especially with several players like Militao and Carvajal who are certain to not be there until the end of the season, Madrid should now start planning for several new players apart from regenerating players, this is also intended to make the players more so that when one player is injured, a replacement is ready for them and this will not interfere with performance because of the many gaps they have.