What you said is very logical for Real Madrid and also for Ancelotti to think carefully as the coach of Real Madrid. Because previously Real Madrid also had better reserve players so that their performance was not so affected when their main players were injured. But for this season it seems to be a bit different so Ancelotti needs to find out where the problem is and try to solve it as soon as possible before Real Madrid really loses the chance to become champions again this season because they are late in fixing the problems that are happening in the team.
Real Madrid are facing some challenges this season including how they can continue to maintain their position and also their consistency in the league and Champions League when the storm of injuries is the main problem, but for those of us who have known and seen how Ancelotti extensive experience and have the capacity to overcome every problem.
When you win the league and UCL quite often, you get a bit of a leeway from the fans and this is why the yare not worried. Ancelotti won two UCL titles so far if I am not mistaken, and two la liga titles as well, this is good enough for him to keep his job even if he doesn't do great. Remember prior year? City won the UCL and Barcelona won the la liga with Xavi, that means Real won nothing and they waited because one year later, even without a striker, they still did great.
So, even if they have one bad season and end up not winning anything this year, they will still be feeling fine because they know next year they can win everything. This type of feeling the fans have for the team allows the players and staff to not have pressure, since they already gave the fans what they want recently, they can go one year without winning, and this is great. Only one who is feeling the pressure is Mbappe, who came in here to win, and if he fails then he will be upset and feel not delivered enough to fans.