You’re right to say that Christianity’s teachings provide a good model for a moral life, but this is not the essential part of Christianity. At its centre is relationship with God, established by the death and resurrection of Jesus Christ. Life lived in right relationship with God will be moral.
However, there’s more to it than that. We need to ask why Jesus had to die. Jesus had to die because we don’t relate to God the way we should. We don’t acknowledge God’s rule over our lives as our Creator, but live for ourselves. And the punishment for this is hell. We don’t deserve hell for not accepting Christ, but because we’ve rebelled against God. In one sense, hell is God giving us what we want - existence outside of his loving provision of all things good. From our perspective, our rebellion may seem not that bad, but from the perspective of the loving and just God who brought us into being, gave us life and continues to provide us with all that we need to live, and so much more, our rebellion is a very serious matter.
It’s like the mother of a murderer. When the verdict is handed down she sees the punishment as too severe. But what about the mother of the victim? They will think no punishment is too severe. Our problem is that we do not look at God’s judgement from his perspective but from ours. We don’t want to think that everyone who has disobeyed God deserves hell.
But God doesn’t enjoy sending people to hell. On the contrary, God tells us in the Bible that he is grieved by the punishment his people deserve for their rebellion. He doesn’t want anyone to perish. And that is why God sent Jesus into the world, to take the punishment for our rebellion in our place, at great cost to himself. By trusting in Jesus’ death in our place, anyone can be rescued from the punishment for being rebels. God doesn’t gloat over the punishment we deserve, but has carried out a rescue plan. So we do have a choice - to trust that Jesus has suffered hell in our place and be rescued from it, or ignore this rescue plan and go there ourselves. God is a God of great love as well as justice.
Furthermore, because Christ has paid the penalty for our rebellion against God we are free to live the way God intended us to live, the moral life you talked about which the Bible sets out for Christians.