"Will people who have never heard the gospel all go to hell because they haven’t heard about Jesus Christ?"

No one will go to hell because they haven’t heard of Jesus Christ. The heathen will go to hell for murder, rape, adultery, lust, theft, lying, etc. Sin is not failing to hear the gospel. Rather, "sin is the transgression of the Law" (1 John 3:4). If we really care about the lost, we will become missionaries and take the good news of God’s forgiveness in Christ to them. See John 16:9 footnote.