The people who back Vini do so because they watched him arrive as a nobody and grow into the guy who dragged Real Madrid through big matches. He earned that love at the club.
Meanwhile, the hardcore Mbappé fans didn't fall in love with what he's done at Real, they were already Mbappé's fans before he even arrived.
So this isn't "Vini FC vs Mbappé FC." This is Real Madrid supporters vs Mbappé fans who only watch Madrid because of him.
But above all, how can actual Real Madrid fans, the ones who watched Cristiano, Özil, Benzema, Bale, Isco, Marcelo (none of whom were famous for insane work rate, quite the opposite for some) pour their hearts out for the badge, press, track back, make the right pass... how can they watch Mbappé and think "yeah, this guy respects the club" ?
The dude just isn't invested. It's not even a talent issue, it's an attitude problem on the pitch. It's like going to watch your kid's U7 game and seeing him just stand there, not moving, not defending, not passing, completely checked out, he probably has the level to play with the others, but he doesn't give a shit about the team, he just wants to go home (or Italy in Mbappé's case).
Put literally any decent 9 who's actually willing to play for the badge up top and the team won't score fewer goals. That's the reality.
I'm not satisfied with Vini either when he doesn't run/defend/press. But notice how he actually does run when Mbappé isn't there. When he knows the players around him are ready to go to war, Vini will fight with them. Mbappé? He simply won't run... and then complains anyway.
Take Mbappé out of the starting XI ,then wins like the one against City in 2024 (the one that went to penalties with Lunin, where the whole team defended like animals) become possible again. Otherwise, every year we'll be playing 10 vs 11, leaking goals left and right, and blaming the defense, the midfield or the goalkeeper as usual.