The electoral college had literally nothing to do with slavery, and everything to do with balancing population-based governance and state-based governance (i.e. the reason we have both a House and Senate).

The 3/5 compromise was used to calculate the population-based component of governance, and at any rate, is no longer used so completely irrelevant today.

I gave more details is this response: https://news.ycombinator.com/item?id=12969671