Every other player might well have a spade and therefore a flush. You might get lucky - in this case, you might be the only player with spades - but because there are three spades in the community cards and you’ve got two spades (4 and 6), that means there are 8 other spades that are either in the deck of cards or with other players (including the king and queen).
This is because, to get a flush, there must be at least 3 cards of the same suit in the community cards.
The problem with flushes is that, pretty much by definition, other players are going to have flushes.
