Tam The easiest way to describe Vinicius is that he has all of Saka's qualities, but he also has elite pace and explosiveness which puts him a level above Saka. That's how good he is, and why this would be such a big deal. The difference between him and other world class players is like the difference between Saka and Madueke.
Back when we had Henry in his prime I used to look at other strikers and think it was like they were playing in a lower division compared to him, even great ones like Kluivert at Barca, Raul at Real Madrid or van Nistelrooy at United. That's how big the difference is between Vinicius and normal top players too.
He's not perfect: he can be temperamental and petulant, and like all Real players he's a diva. He's among the 2-3 players who dribble most in the world and most successfully, but it also means he drops the ball a lot. Like Henry he doesn't do defence, so someone else - that'll be Saka if he comes here - will have to sacrifice themselves and do that work to cover for him, but they'll do it because he's so good at what he does, and what he does is producing the kind of moments that win football games. His consistency in that regard is remarkable: in eight years at Real he has never had a bad season. In the last five years he has produced > 40 goals and assists per season (our biggest contributor last season was Gyökeres with 27).
Vinnie just had rotten luck that the best player of his generation showed up at Real Madrid two seasons ago and likes to occupy the same exact same space on the left as he does. Otherwise he'd be the main man for the biggest club in the world right now.