Walmart and Target also do the marketplace stuff.

Costco is great for curation, but only for the items they carry.

A combo of Amazon for the random junk I don’t care much about and Costco for consumer staples works out well.

And no online vendor gets remotely close to Amazon for speed of shipping, ease of returns, and product selection. Usually matches the best price I can find on most things too - outside of stuff I buy direct from China.

Lots of the random crap I buy on Amazon I want the marketplace for. Like I needed a dozen plant domes this spring. I wanted them tomorrow, not next week and I didn’t need qty 100. So having the option for that vs. a gardening warehouse that targets large growers is quite handy and exactly what they excel at for me. I could care less which random brand sells the thing to me since they are all the same.