If Harris loses, I don’t think the appropriate response will be “where did the democrats get tactics wrong?” I think if she wins the popular vote, but loses the electoral college, it will be about how our system doesn’t work when we have partisan, geographic sorting.
If she loses outright, it will be about how we failed to convey the danger of Trump. It will be about how we have lost a shared notion of truth. It will be about how we’ve lost a common information architecture and with it, our common reality.