Foodchain doesn't require the player to reach 7 mana, only that they spend at least 7 mana in one turn.

From my personal experience It seems FC decks fell out of favor recently. I hardly see them anymore. But that doesn't mean they will never become popular again.

A lot of people dislike the deck because the win condition is mostly based on luck, not skill, and is very hard to deal with without specific counters in hand.

There isn't much to be done in Ranked about this, but at least in Formats you can expect the card to remain consistently banned.