Aristotle fed off Plato's values which were downright theistic. Aristotle failed to establish First Causes of his values apart from Plato, which is why modernists pretty much ignore the poor guy except to trod him out when he serves their purpose.
And one step beyond Plato, is Socrates.
So the most you can say from the example of Plato is that theistic belief is not necessarily a deal-breaker in formulating moral valies.