Luke 16 tells about the rich man and Lazarus. In Hades, which is not hell but the place of the dead, is described as side with comfort, a side with torment and with a great gulf fixed in between. Jesus went to hades, Acts 2:27 but to the paradise side, Luke 23:43. Some speculate that before the saving blood was shed, none were allowed to enter heaven itself. Paul seems to teach that when the faithful die, they go to be with Christ, Phillipians 1:23 (and other places).

Atheism is only a temporary condition. Judgment is coming. Many sincere people who call Jesus their Lord will find themselves in the same condition as every atheist, lost.

Nowhere in scripture is anyone ever told to just accept Jesus into your heart. Nobody is ever instructed to say a sinner’s prayer. Every actual example of conversion (found only in the book of Acts) is similar and nobody ever is told to accept Jesus into your heart.

“"Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. On that day many will say to me, 'Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?' And then will I declare to them, 'I never knew you; depart from me, you workers of lawlessness.'”
‭‭Matthew‬ ‭7:21-23‬ ‭ESV‬‬

“And being made perfect, he became the source of eternal salvation to all who obey him,”
‭‭Hebrews‬ ‭5:9‬ ‭ESV‬‬