The part about Costco choosing to avoid the last mile shipping problem reminded me of a proverb, roughly translated as: A clever person solves a problem; a wise person avoids it. I think it holds a lot of truth in engineering.
Both spectrums are hard. Solving last mile is really really hard, but if you do that's a huge moat (aka Amazon). If you avoid last mile, you best deliver value in some other way, which Costco does by giving you more per dollar than anyone else.
For me, Costco has good prices, an excellent return policy, and reliably excellent quality. I don't need 15 choices of peanut butter, just a few (smooth and chunky, natural and sugary) good ones.
I also appreciate that Costco employees are always busy, but they seem positive and friendly. Most Costcos I go to, I look for the board that highlights long-term employees. The one nearest me has 8-10 people who have been there for 30 years or longer.
As the article said, Costco pays higher hourly wages than most other people. They also provide extended health benefits (in Canada, so basic health is already covered), paid sick days, paid vacation days (one woman I talked to had been working there for 25 years and had six weeks of annual vacation!), and more.