In the past 3 years, Amazon's brand went from gold to gutter trash. That's something which took 2+ decades to build up. User drain will follow.
This would be a good time to build the next Amazon, if someone has a few $B to spare. Basically, just do the same thing Amazon did through 2020, only more quickly, cheaply, and efficiently the second time around without legacy code / contracts / employees / etc.
If an Amazon replacement (A Inc) is shipping a 3M product, it should go directly from 3M to an A warehouse, and from there, to me. The supply chain should be trusted. I don't think A should try to be a marketplace where anyone can go in, and sell "3M" products which then get comingled.
If a vendor wants to sell on A, someone from A should, at the very least, have a conversation with them, look up their corporate registration, etc., and make sure everything is legit.
If there is a report of a scam, A should look into it every time. I think this is really where Amazon fell apart. Scammers should not get away with it. Right now, if I get scammed, those same scammers keep selling, even under the same name.
Pricing should be set not to be the lowest-cost vendor, but the lowest-cost vendor _with reasonable support_, including and especially investigating scams. The reason to look into a scam isn't to support me, but to avoid needing to support the next thousand people, and the reputation harm that comes with that. Scams and other issues should not have costs externalized to the customer. That sets internal incentives right.
Amazon did this adequately well pre-covid, and most online stores (which is not the same as marketplaces) don't have the same set of problems. Amazon has drifted from being a low-cost / high-service / good logistics competitor to Target, Walmart, etc. to being a high-cost competitor to eBay and Aliexpress.