For me, it divided into 'regular fans' and 'unexperienced immature dense fans'.
And it's not about thinking it's a lot of money, because everyone knows that it IS a lot of money... It's a matter of knowing about the business, knowing about the maket, knowing how the economy has been in past 10 years and how it is going to be in the next 5.
If you (not you, op, i'm talking about whoever reads this) are as simple/dense/stupid enough to straight up disagree with his signing because 'it's too much money for a unproven kid', you better stick to r/soccer or at least try to understand/believe those who are aware of what's happening.
You don't need to believe he is going to be the next Pele or whatever, you have to trust the decision from the board which is of smart/planned changing of transfer policy based on how the world of football is now and how's going to be in the next decade.
Brief explanation to those who still don't get it:
1) We don't need 45Mi. Even if we throw away 200Mi tomorrow, the club will still be the same, spending 45Mi won't hurt in any way our plans and business. considering the current Market, there's not many starters that we could just upgrade by buying another player, unless we spend 100-200Mi in huge and kinda unecessary names like Messi (that if their teams even accept selling). We just won UCL, there's no need to strength the current roster with more stars, nor spend big on them, we need to take care of the mid and long-term future.
The stadium will be upgraded, the facilities are already state of art... The only things that could be improved and weren't already it's not a matter of lacking money, it's business/administration decisions.
2) The way the market is (and mostly how it's going, how things will be in 5-10 years) we can't just want anymore, we can't just let smaller clubs (specially Bayern, Barça, English clubs, etc) develop all the young talent and then be forced to buy them for 100-200-300Mi. Because that's whats going to be like in a decade. If we want another move like the Cristiano's transfer, the fee will be way over 100Mi by then. The transfer policy HAS to change because that's how the market is shaping... Even guys like Pogba, Mbappe, Aubameyang and such, if we go after them right now, i don't see how to buy either of them for less than 70Mi, that considering they are still not on Barça-Bayern, which would make it pretty much a impossible transfer.
It doesnt matter that our club is the biggest. The way things are going, the prices will be too high in a few years. If Vinicius be a world class player by then, 45 will be nothing, just like Cristiano's fee was crazy at the start and today it's cheap.
If he flops, he flops. That's it, 45 Mi won't hurt the club, it was a great risk taken and i'll back up this move forever not because i fully believe he will succed, but because i understand how the business and finances are happening in today's football and Flo (and the board) made a great decision.
3) It's crazy for me how most of the people who never heard of him are calling him 'just an unproven dude who barely played with main team'. It's obvious, he's 16, everyone in that age is unproven. BUT it doesnt mean that he hasn't show anything, he have been playing international tournaments with the under-15 and under-17 Brazilian national team and have been absolutely dominating it. He's getting every MVP award, every goalscorer award, titles, etc.
I bet some of you already watched some youtube videos of his highlights, right? those are all from the most recent tournament, the one that was broadcasted by brazilian tv. In a single tournament there's like 10 minutes of highlights of him. I know highlights doesnt mean a lot, but there are reasons why he's hyped, You all know how Neymar Takes over the game when he's playing with br NT? that's mostly how Vinicius plays in the underX teams, he demands the ball and take over, several creative and dangerous plays in a row, always confident and productive. Or you all really think you follow/watch/know more football than Real Madrid's scouts?
Will he be ballon d'or, who fucking knows, i'm not saying that, i'm just saying that 'he's unproven' argument is r/soccer level of bullshit, you guys have to keep in mind his performances and numbers with the youth caps that he had.