The operative adjective in Matt 24:39 is ἅπας (hapas) = "all, the whole, completely". The meaning of this word can be drawn from three lines of evidence:
Source #1 - Matt 24:38, 39a
For in the days before the flood, people were eating and drinking,
marrying and giving in marriage, up to the day Noah entered the ark.
And they were oblivious, until the flood came and swept them all
away.
Note that the "all" in V39 refers to the "they", that is, the people who were "eating and drinking, marrying and giving in marriage"; that all the people of the earth who were going about their daily loves oblivious to the coming calamity
Source #2 - Matt 24:39
... So will it be at the coming of the Son of Man.
The "all" refers to the same class of people who are oblivious at the end of time at the coming of the Son of Man (Jesus), ie, all those who will be swept away, viz, the wicked in both instances.
Source #3 - Gen 7
Jesus' prophecy in Matt 27 is clearly alluding to the record in Gen 7 which reads:
19 Finally, the waters completely inundated the earth, so that all the high mountains under all the heavens were covered.
20 The waters rose and covered the mountaintops to a depth of fifteen cubits. 21 And every living thing that moved upon the
earth perished—birds, livestock, animals, every creature that
swarms upon the earth, and all mankind. 22 Of all that was
on dry land, everything that had the breath of life in its
nostrils died. 23 And every living thing on the face of the
earth was destroyed—man and livestock, crawling creatures and
birds of the air; they were blotted out from the earth, and only
Noah and those with him in the ark remained.
This is not describing a local flood, but a universal flood by the repeated emphasis of entire destruction of all living things.
Thus, Jesus confirms this by describing Noah's flood to be universal destruction of the wicked, just as it will be at the coming of the Son of Man, Jesus.