Of course they're not really valid. Neither is the Ballon D'Or for that matter. They include forwards most of the time, but you have to agree that forwards are the most valuable players in general. We can talk about this being right or wrong, but it is a reality that forwards take the cake when you talk about most valuable players. The value of the player is being decided by the market. Alexis probably worths around 60m euros now, that is the sum he'll go for if Arsenal decide to sell him.
Of course it's a collective sport, the whole talk is theoretical, and in practice you never know how important player X or Y really was, since you can't know for sure what would've happened with another player instead of him. But to me at least, I think we would have won the treble with other good players instead of Raktic (same goes for other 3-4 players in the team). Rakitic wasn't quintessential for our treble, like Messi, Suarez and Neymar. I love Rakitic. I think he's our most improved player since the start of the season (not counting Suarez), and he did have an impact in the team, but not the kind of impact other top players couldn't have provided as well.