Those after the Cross Will need Jesus to enter into Heaven.
There are not any who will not have heard about Christ.
Those after the Cross Will be judged by God's Word - If they failed to get right by the Father through Christ Jesus then there is nothing left to help them.
Sinners or unsaved can love those around them - that will count for nothing without Christ.
Matthew 24:14
And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
Everyone After the Cross Will have had a chance to Accept Jesus as payment for their sins.
Blessings
FCJ
Consider Romans
Romans 2:12-16
For all who have sinned without the Law will also perish without the Law, and all who have sinned under the Law will be judged by the Law; for it is not the hearers of the Law who are just before God, but the doers of the Law will be justified. For when Gentiles who do not have the Law do instinctively the things of the Law, these, not having the Law, are a law to themselves, in that they show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them, on the day when, according to my gospel, God will judge the secrets of men through Christ Jesus.
This is not only looking back to before Christ. It applies to, for example, the indigenous people of the Americas before Columbus. And there are still many places where the Gospel is actively warred against, and although there may be secret groups that serve our Lord, there are many persons that have never heard. And, even in a relatively free society (such as here), one cannot assume that all have heard of Christ. This is why we need to continue to proclaim Him to those around us.
As to how a non-believer could "do instinctively the things of the Law" as Paul states in Romans, one needs to go no farther than Matthew:
Matthew 22:35-40
One of them, a lawyer, asked Him a question, testing Him, “Teacher, which is the great commandment in the Law?” And He said to him, “ ‘You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.’ This is the great and foremost commandment. The second is like it, ‘You shall love your neighbor as yourself.’ On these two commandments depend the whole Law and the Prophets.
In any case, it is the blood of Christ that saves the sinner. Those with knowledge of God's Law because the Law is satisfied by that sacrifice. For those who did not know the Law, but acted according to the words of Jesus, the Lord extends His grace to apply Christs sacrifice to their sin.