Your analogy helps focus the crux of the problem. How many malls have all their stores branded as the mall?

Amazon have been so successful integrating stores into their site that customers don't realise who they're buying from.

I'll argue that the branding issue is a distraction. Shoppers generally understand that Home Depot, Walmart, etc. don't make or comprehensively vet everything they sell, yet they still stand behind the customer experience via returns and support. I find holding Amazon to a higher standard of product vetting as compared to other mass retailers a difficult position to defend.

Holding them to exactly same standard as all retailers. It seems US and EU law may be vastly different on this front. Here it's the retailer held responsible for problems, so it's in their interests to vet as a normal part of the buying process, and they do.

New Company will find product looked at to decide if it's worth putting in the stores, that they meet electrical safety or whatever laws etc.[1] Only once approved will they be placed in store. They'll probably trial in just a few stores first. At least some retailers have an audit process for the factory too.

[1] https://www.homeretailgroup.com/suppliers/how-to-be-a-suppli... 80,000 lines, they say they assess all products, and mention lab testing and pre-shipment inspections. They're a mass market retailer with a lot of product at the cheaper end of the scale.

Amazon is not really much like a mall; insofar as any brock.and mortar analogy is applicable, it's more like a retail store where some of the items on the shelf are sold on consignment for third parties, while some are regular first-party retail. Which isn't an entirely unheard of thing, though in brick and mortar it's probably more common for antiques, etc., rather than new consumer goods.

I'll completely agree that the analogy is imperfect. Yet it only has to stretch this far: it's just as bad an idea for a mall to literally vet every item sold by its retail occupants as it would be for Amazon.

In fact, no retailer does this. Consider any direct seller of a wide assortment of retail goods, e.g. Home Depot, Walmart, etc. None of these have rigorously "vetted" every item that comes through their doors. They certainly get problematic goods, and deal with that after-the-fact two ways: to purchasers via customer returns and support policies, and to suppliers via feedback into their supplier relationships (give us bad stuff, our $$ go elsewhere; contracts; etc.).

The idea that a retailer should be held a priori accountable for third-party goods it sells smacks of the same kind of thinking that suggests ISPs should be held accountable for third-party content flowing across their networks.

Any merchant selling goods is accountable for the goods it sells (implied warranties) and this accountability may not be avoided, in some jurisdictions, even by express disclaimer.