Every man woman and child have sinned.
Romans 3:23
for all have sinned and fall short of the glory of God
Yes, there are babies who die at childbirth but that is an exception because they are innocent and have not yet sinned.
Because everyone has sinned, we all deserve punishment for sinning. It is not right for God to let people into Heaven who have sinned is it? Just like it is not right for a Judge to let all the criminals into society. There must be punishment.
1 Corinthians 6:9-10
Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor male prostitutes nor homosexual offenders nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God.
Revelation 21:8
But the cowardly, the unbelieving, the vile, the murderers, the sexually immoral, those who practice magic arts, the idolaters and all liars—their place will be in the fiery lake of burning sulfur. This is the second death.”
There is two deaths, the first is when you die, the second comes after you are condemned - it is Hell.
Romans 6:23
For the wages of sin is death [second death - Hell], but the gift of God is eternal life in Christ Jesus our Lord.
Basically, we are all condemned men. But God set apart his son who has never sinned and he died on the cross on our behalf, he took what should have been our punishment.
Because this has been done, we can now have all our sins wiped clean.
All one must do is believe in Jesus and what he's done and repent for your sins.
Acts 3:19
Repent, then, and turn to God, so that your sins may be wiped out, that times of refreshing may come from the Lord,
P.S. Thousands herd and seen the powers Jesus had when he walked on this earth but even that was not enough to make all the people believe in him. In fact they ended up crucifying him.