Ezekiel talked about a forest fire that would burn up every tree. But the people complained he was talking in riddles. So he spoke instead of God's sword that would slay the "righteous" and the wicked alike.
Why is it so important to remember the Flood? Because it's a pointer to a far greater event - the ultimate catastrophe for the ungodly.
The leaders of Israel in Ezekiel's day had treated God wickedly. But they felt no shame nor remorse. Yet the Lord promised that one day his people would loathe themselves for their sins. That takes a new heart, a new birth!
The false teachers were happy to quote Genesis but conveniently overlooked the story of the Flood. Why? Because they preferred not to believe in a God of justice and wrath.
Ezekiel took the elders of Israel through the history of the nation. What was the chief lesson they could learn? That they had never learned from history!