eBay makes it much clearer what’s going on. There are some things I buy there with the full knowledge that it’s coming from some rando, probably in China. I limit what I buy there to products where that’s ok. With Amazon they make it look like many products are more than they really are.

That's one of many problems. Fake buyers winning auctions with no intention to pay, fake buyers putting high bids seconds before the auction end to reveal everyone's bid limit, then cancelling the bid, then bidding £1 below the highest bid limit to max out bid limits. The UI is a train wreck with not a single page vaguely consistent with the others, not just the format, the content too (messages pending, items sold, etc).

I buy and sell a lot on eBay. I just always use buy it now. That solves all of your complaints above. (just make sure you require immediate payment).

As for the UI, I agree on that. But Amazon's seller UI is a nightmare as well. Many listing features don't even have a UI and require a huge bloated Excel file upload.

EBay doesn't have inventory co-mingling.

Okay. What's your point?