If not for the arrival of Mbappe, Vinicius was the best player in Real Madrid that you can count on whenever Madrid needs a win in any match. You should see how important and good he is at his to the extent that Ancelotti have to convert Mbappe into a central forward instead, of allowing Mbappe play to play on Vini's wing. Vini will not be sold because the club needs him more than the Arab men.
Vini is no doubt an important player for Real Madrid in both Ancelotti and this present Xabi Alonso's era if he wasn't Xabi would've tried to offload him just like he's doing with Rodrygo currently but he has a major role to play for Xabi Alonso when the season start that's why he's untouchable. Real Madrid is yet to bounce back hopefully we'll see a different Madrid when the new season starts, but right now Xabi has lots of work to do in the preseason by drilling his players to improve better and give their best ahead of the new season he also has to use this period to know the suitable positions that would suit soke players and help them do better.
The real problem for Real Madrid is their midfield woes. As we saw last year, Kroos' absence significantly impacted Real Madrid. To avoid a similar problem this year, I believe they need to make a transfer in this area. Vinicius, Mbappé, Rodrygo, and Bellingham are all effective attacking players for this team. However, they lack a master of control in midfield. A transfer in that area would raise the team's level. However, they probably haven't figured out who to bring in for this position. I'm sure manager Xabi Alonso has a plan.
What you said is true. It is the midfield control that he really needs to do something about. kroos is not just any how player, his pattern of play is very unique so it will be hard to replace him. No matter how good Bellingham is, he can't be compared to kroos in terms of how to control ball. The attack is really good with vini ,Mbappe and others, however if the midfield is not strong it will also become a problem. They should get a good replacement . I believe xabi Alonso have a good experience and would definitely get a good replacement.