There are still rumours that Real want to sell Vinicius as early as August, which means that Alonso still sees that there is no good link between these players, so there is no point in trying to build something further around them. Although last season I didn't notice any conflict between Mbappe and Vinicius, they worked well together and brought victories to Real Madrid
The was no "conflict" because for some good parts of the season the did not play together due to injuries but whenever they would play together, one of them would not shine as the left-hand forward side is a favorite one for both.
In that case if this continues to be the case then obviously they won't play together any further, Alonso is not going to be ceremonious with these players no matter how much they cost or how important they are to the club, for he has a goal of winning. But even if the situation doesn't get better, Real are capable of reaching the Champions League final, that's Real
I don't believe the rumors of a rift or a bad relationship between Mbappé and Vinicius, as the media has been constantly highlighting these issues since Mbappé's arrival at Real Madrid, but they're not.
Mbappé and Vinicius are two key players in Real Madrid's attack. This is just a rumor, and I'm confident they'll both stay at Real Madrid. Xabi Alonso is also a brilliant and authoritative coach; he'll surely be able to unite these two players to improve the team.
All I see is them fighting for advantage amongst themselves. Yes, they still score, but the utility from them playing together is not as great as it was before they teamed up. I think Alonso's first priority is to win La Liga first and then think about the Champions League, simply because it's a harder tournament and if he doesn't get Mbappe and Vinicius together it will lead to failure