No one has entered Heaven except for God, Jesus and his angels. Since the falling of God’s angel Lucifer (AKA the devil) God made it so that no one could enter Heaven unless they’ve passed their test on earth.
Jesus lived a life free of sin and he never sinned once, he was also the one and only son of God, hence why he ascended to Heaven when he died.
Everyone awaits Judgment day, whether dead or alive, those who inherit the kingdom of God will inherit it at the same time.
Think about it, it would simply be unfair for people who die to immediately inherit Heaven when others are still on earth, for the earth we live on is nothing compared to what God has for us in Heaven.
“For God shows no partiality.” •Romans 2:11•
When people die, they go into a phase of resting whilst they await for judgement day.