The reason Jesus descended into hell for three days was to preach the message of salvation to all the generations who lived before He came to Earth, not pay for them. He paid for all sins by dying on the cross.

People lived and died on Earth for four thousand years before the birth of Jesus. All without a chance to accept Jesus’s sacrifice for their sins. The only nation that had sufficient knowledge of God before Jesus came was Israel, and even those had to rely on their own works for salvation. It’s to be fair to all those generations of people that Jesus descended into hell for three day, and did a mass evangelization event in hell.

 

Those people who were born after the gospel was brought to Earth, and have heard it, would be judged based on whether they accepted that gift or not. 

 

Jesus did everything He could to help people not go to hell. If He made it any more easier, He would be violating the law of free will. All people have to do is accept Jesus as their saviour. If they don’t even want to do that, God respects their free will, and won’t make them go to heaven.