That is definitely true, they reacted as if Ancelotti was a terrible manager during his sacking, but the reality is simple, he won 2 UCL and 2 la liga titles while he was there, and I am sure some cups too that I can't really think of. There aren't really anything else that we could see about this situation.
So we can't really see the current situation suddenly better, because while Xabi has proven himself at Leverkusen, Ancelotti also won 50% of the la ligas he managed, 4 years, 2 titles, and same for UCL as well. Without injuries, he would have probably do a lot better next season as well. There aren't that many situations that can get better, Ancelotti could do great this season as well, considering the team, as long as they stay healthy. So, Xabi has a huge chip on his shoulder.
I think that if Ancelotti had stayed at Real, he would have had a few more good seasons and would have won a few titles, because now the defenders are back in training and preparing for the new season. Perhaps Ancelotti thought that they would return earlier, when he was in no hurry to buy new defenders, but the season turned out to be more difficult than he expected. It should be easier for Alonso because firstly he bought a few new defenders, and secondly Carvajal and Militao are returning to the game, if this is not enough for him, then I don’t know what else can help him.