While you're not stating it explicitly, this makes various assumptions that I don't agree with. But the basic question is reasonable. Why does God not simply make everything right, using his authority? I don't know, because I don't know how God makes decisions. My only response is that the nature of Jesus' teaching, and the way God works in the OT, all suggests that he works only by persuasion. That leaves lots up to us, and inevitably things sometimes go wrong. But some of the things in the Bible surely didn't happen. E.g. the genocidal wars in the early books are from periods when there's not much historical content to the Bible. Archaeologists say that Israel moved into the Holy Land slowly and largely peacefully. On the other hand, there's plenty wrong, even today. Why doesn't God simply fix it? The best answer I know is that the kinds of people he wants to produce need real challenges and real consequences in order to develop. (This assumes that he's omnipotent, an assumption that can't be discussed in this forum.) I don't believe, however, that he consigns most people to hell. Discussions about hell aren't really permitted in this forum, so I'll simply say that in my view it's not likely that very many people end up destroyed. (Take a look at discussions in Controversial Christian Theology if you're interested in what CF readers believe about hell.)
I am very skeptical about the idea of the Fall, and the typical Christian concept of what salvation is about. What we know about history and the origins of humanity make Genesis 3 impossible as a literal account. Humans evolved to be creatures that learn from mistakes. We were never perfect, and weren't intended to be. As long as we accept that fact, and admit our errors, I think we're OK with God. Jesus' teachings on judgement suggest that the people who are rejected are those who blatantly reject the good of others, or reject Jesus' message. I hope there are few of those.