> There's a lot of stuff to nitpick in the christ story but I've always thought they did a particularly poor job of justifying the sacrifice as being required.
Are there? Or are these gaps of knowledge?
For instance, you claim that "they did a particularly poor job of justifying the sacrifice as being required". The first problem is that no one claims it was absolutely necessary. God is not compelled or coerced by anything greater or outside of him. This is why I wrote "an act that is not necessary, but as Aquinas says, most fitting". It is most fitting as part of a freely chosen, greater providential plan that you can say best manifests the divine nature and especially in relation to mankind. You might call this a necessity relative to this plan or under the presupposition of this plan, but it is not absolutely necessary. God could choose to forgive sin with a snap of the proverbial fingers.
> I suspect it resonated more strongly with people of the era whose primary mode of interacting with gods was via sacrificial propitiations, modern relgions rarely stress that part.
What are these "modern religions"? New Age cults? Various Westernized consumerist varieties of Buddhism? Occult stuff like theosophy? Other neopagan attempts to retreat from history back into myth? Whatever they are, and putting aside principled criticism, their "modernity" already works against them, as empirically, it can take a little time for the inner faults of a worldview or religion to result in tangible crises. History is littered with all sorts of cults and heresies that have since long been swept into the dustbin of history. Does anything remember the Cathars, the Gnostics? (Curiously, we're experiencing a bit of an unwitting gnostic revival now in secular Western culture. Once you see it, you can't unsee it.)
In any case, modern ideologies often gladly dismiss the sacrificial demands of justice, because they first dismissed sin. And they dismissed sin, because they did not wish to think of what they desired to do as sinful. It chafes and eats at the conscience and contradicts a certain desire for a kind of ontological autonomy, which is to say, self-idolatry. But denial of sin - with sin as an choice taken with some degree of conscious assent - is always a bad move. Repressing such knowledge or losing the vocabulary to talk about it only places you in helpless submission to it. Every sin causes a disintegration of the self, however minor. The universally observed and conspicuous pre-Christian sacrificial propitiation of ancient peoples may have been mythological, but it drew from the well of the human psyche. (The tradition of the Church would say they prefigured the true and perfect sacrifice of the mass. Even here, many low-information Catholics, encouraged by the opportunistic cultural upheaval after Vatican II, have absorbed modernist sensibilities, failing to recognize that the mass is, above all, a sacrifice made on an altar.) There is no justification for the belief that modernity has somehow transcended the human condition and banished human nature. We have merely obscured the meaning of certain impulses at our own peril, dressing them up in what is often a flaky pop-psychological terminology. We still project guilt and scapegoat. We still experience the impulse, but without the proper outlets, it becomes a destructive and self-destructive force. The demand for sacrifice still exerts pressures on the psyche, whether it is acknowledged consciously or not, resulting in all sorts of weird and pathological behaviors and mental states.