If few go to Heaven then, logically, most go to Hell. Thank you, God.
It does indeed seem to mean at least a majority, though I'm aware I'm not able to assess other's hearts, which would require a form of omniscience. But we learn even what we may have presumed about what groups will be saved are usually too simplified --
For instance, many object to the Flood killing presumably many younger and still innocent people, and not only the guilty majority (totality of adults?) already engaged in "...every inclination of the thoughts of the human heart was only evil all the time. .... and the Earth was full of violence" -- e.g. rapes, murders, raids, assaults, genocides, etc., as their normal ongoing activities, their way of life.
We learn in the Bible we learn that after this temporary life is a "Day of Judgement" where the innocent and the forgiven will be separated away from the unrepentant guilty. But can we gauge when it's too late? Not so easily!
In straightforward form, unrepentant means no regrets for the evils they did, no admitting it was wrong to God.
While during this temporary life the rule is:
1 Peter 3:11 He must turn from evil and do good; he must seek peace and pursue it.
But... we learn (though not everyone is aware) that God gave them a 2nd chance even after their deaths in the Flood (and by extension it's thought also others not having yet heard the gospel):
18 For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit.
19 After being made alive, he went and made proclamation to the imprisoned spirits—
20 to those who were disobedient long ago when God waited patiently in the days of Noah while the ark was being built. ..." (1rst Peter chapter 3)
Though unrepentant in their evils they did during life, they nevertheless we learn got a 2nd chance to turn and repent. Because they had not gotten the chance of the saving work of Christ, and now they have gotten that chance.
So, you can begin to see how then:
6 God “will repay each person according to what they have done.”
7 To those who by persistence in doing good seek glory, honor and immortality, he will give eternal life.
8 But for those who are self-seeking and who reject the truth and follow evil, there will be wrath and anger.
9 There will be trouble and distress for every human being who does evil: first for the Jew, then for the Gentile;
10 but glory, honor and peace for everyone who does good: first for the Jew, then for the Gentile.
11 For God does not show favoritism.
12 All who sin apart from the law will also perish apart from the law, and all who sin under the law will be judged by the law.
13 For it is not those who hear the law who are righteous in God’s sight, but it is those who obey the law who will be declared righteous.
14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law.
15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.)
16This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares."
Romans 2 NIV
So, basically, no matter what you have heard in oversimplifications, we are not able to say who will be saved, and who will not (though many try to oversimplify), except only the most basic parts, they they must repent of their wrongs, and that God is merciful to those that repent....