Depends on what you mean by "sustainable" and what exactly you are referring to. If by sustainable you mean relevant, meaning the teachings can stand on their own two feet as the gold standard for modern society to abide by, then yes, but if by sustainable you mean its teachings can actually be maintained, then no. If the teachings could be maintained, the old monarchical, Israelite kingdom would still be going strong to this day. If the teachings could actually be maintained, there wouldn't be a need for an atonement. The fact that an atonement was necessary only shows that something was broken, that something needed to be fixed, or changed, in a sense. There wouldn't be a need for an entirely new creation if it could truly be maintained. The whole narrative would stop at his resurrection and the great white throne judgement, and left it at that, but it doesn't.