I recently read the Theodosian Code among other things, and it seems to me that their social, economic, and political reforms relied to heavily on coercion and resulted in loss of individual freedom. That was one mistake. I also think Diocletian goofed by setting up a tetrarchy (rule by four) instead of a trinity. Constantine had it halfway right. In my view, success requires Christianity and freedom. This also is a subject we can debate some other time.
Theodosius was much later than Diocletian and had no direct contact. Individual liberties were greatly constrained at the time of Jesus anyway, unless you were a Roman citizen, and even then...
However, we're all hijacking this thread. The original question was whether a value-free society can be saved or redeemed. History's answer is yes - though it would be painful and the price would be high.