There are so many places in the Bible where some are tempted to veer away from the straightforward meaning because something else seems so attractive. That Noah was the one last genetically pure human is a very provocative thought for some, UNLESS you make that assumption that his wife, and his son's wives were also genetically pure, then it doesn't matter, does it?
And besides, the Bible says this happened after the flood as well. Jewish tradition is that the angels came down on Mt Hermon, I think it is.
If we understand that Noah was the one righteous man left, then he, the patriarch, is preserving the worship and ways of God for his family, and their children.
It's like in Genesis 22, where Abraham tells Isaac, "God will provide Himself a sacrifice", many run with it as though God were promising to come Himself to be offered. But it really means that God would provide an offering for Abraham to offer to Him.
Much love!