To your first statement, is this even true of Amazon?

In the US, Amazon Prime has something like 80% penetration into households making >= $100k/year. This move into Whole Foods reaffirms this focus on high-income households, where convenience is often as large a factor as costs.

My hunch is that Amazon has been a massive positive in aggregate, but poor households have been negatively impacted by Amazon, taking into account loss of jobs, lowering of wages, and some positive lower costs for goods.