Generally speaking, there are about 8 or so atonement theories out there, with variants. To me, it’s easier to divide them into two groups.
One group of atonement theories postulate that the problems primarily stem from personal dimension of people (who are fundamentally perverse), and of God (who is fundamentally angry about people.) What Jesus did was more or less redirect the focal point of God’s anger to himself, thus getting us off the hook. The main idea is that of legal transaction.
The other group of atonement theories postulates that the problems to be solved are of systemic nature. They lie with both with human psyche individually (egotism) and socially (systemic oppression and scapegoating). There is also a cosmic dimension to the problem statement (decay and death). What Jesus did is he absorbed the individual, the social, and the cosmic sin (and therefore death), triumphed over them, and created a mechanism of being able to tap into the power to overcome all those.
I would submit to you that the second group of atonement theories has much more coherence and explanatory power. Also, the 2nd group is the one that leads you to living like a responsible, fully empowered representative of God in every area of life. It’s the only one that can underwrite consistently replicable results, and not just occasional haphazard “victories”.
While on the surface the Biblical account in its entirety may suggest that the 1st group gives a good explanation – when you work out the equations, soon enough you will have giant holes in your theology that are impossible to paper over. To cover those up, you have to resort to fundamentally extrabiblical and pagan explanations, usually of “innocent virgin thrown into a volcano to appease angry gods” variety. Recent works by NT Wright and others illustrate this brilliantly. Also, by necessity such theology puts its adherents into fault-finding and moralizing mode vis-a-vis the rest of humankind. Unfortunately, this theological cluster of atonement teachings has been the dominant one in Western Christianity to this day (although it’s changing), and of course with paltry and very uneven results to show for.
Jesus didn’t say “the accused need a lawyer”. There is a legal dimension to the atonement, but that’s a fairly technical legal detail to a much larger infrastructure that Jesus set up. This issue is already unilaterally solved on God’s side, the legal framework is made available to all, with a standing invitation for anyone to simply opt in. Nothing much aside from simple acknowledgement and acceptance needs to be done here. The genesis of Christian religious fundamentalism is exactly in trying to make this legal side into a central and overarching issue of one’s faith confession, with many warring factions competing for the role of official legal interpreters and executors.
Rather, Jesus said ” the sick need a doctor”. Unlike the purely speculative legal side, you can’t just declare a sick person healed without tangible changes being evident. And in order to defeat sin, sickness, and death – Jesus did something that was never done before. Discovering what that “something” is and how it works is the subject of our walk with God. (In Greek, that “something” is referred to as “logos” – i.e., “operating principle behind reality”. That’s a subject for another day).
It takes a lifetime to master how to flow in it in a tangible verifiable way. It will take generations of trained and committed representatives of God here on earth to work the garden of Eden project, which God never revoked or even postponed. But that’s the only thing that theologically makes sense to me today. And that’s the only thing that can underwrite any serious life transformation, on both individual and communal levels.