This depends on your priors. If you assign comparable probabilities to simple and complex hypothesis, this follows. If you assign higher probabilities to simple hypothesis than complex ones it doesn't.

If you flip 1000 fair coins, the resulting output is more likely to be a mishmash of meaningless clumps than it is to be something like "HHTTHHTTHHTTHHTT..." or another very simple repeating pattern. Similarly, a chaotic[1] process like the evolution of our ethical intuitions is more likely to produce an arbitrary mishmash of conflicting emotional drives than it is to produce some coherent system which can easily be extrapolated into an elegant theory of population ethics. All of this is perfectly consistent with any reasonable formalization of Occam's Razor.

EDIT: The new definition of "complex" that you added above is a reasonable one in general, but in this case it might lead to some dangerous circularity - it seems okay right now, but defining complexity in terms of human intuition while we're discussing the complexity of human intuition seems like a risky maneuver.

Wouldn't highly abstract aspects of our psychology be be more recent and as such simpler?

The abstract aspects in question are abstractions and extrapolations of much older empathy patterns, or are trying to be. So, no.

1. In the colloquial sense of "lots and lots and lots of difficult-to-untangle significant contributing factors"