What are the other problems?
Anyways, I'm not defending, just surprised the HN crowd accepts a few anecdotes which are statistically insignificant given the Amazon volumes.
I see questions like, how do people still trust to buy on Amazon? Aren't they aware of all the fraud?
And the answer is no they are not, because they've never been frauded through Amazon, and know no one who has. And that's the case for most Amazon shoppers.
People on hacker news have seen the outliers, the blog post about a single third party fraudster, and a few commenters who maybe experienced something similar.
There are many great 3rd party sellers on Amazon that operate in good faith, and give just as good an experience as 1st party Amazon. But on HN, it seems people see black or white only, and somehow they conclude all black even though the canvas is majority white.
I feel like I'm back in 2000, when some people were asking: How can you trust buying anything online, aren't you afraid of the fraud?
I've ordered countless items on Amazon, in the hundreds, most from 3rd party, never got frauded, never had issues. If you go by anecdotes, add this one to your samples.
The other problems are: third-party sellers pollute the listings with unobtainable low prices, long delays, and shit products I'd never want to buy. It's common for me to find a product on Amazon only to discover that the low price I thought I was getting isn't actually available, and I have to pay some absurd shipping fee with a third-party seller. Or the cost is correct, but it'll take two months to ship. (This just happened to me yesterday with a "Prime two-day shipping" entry!) Or I have to dig past the first page of the search results because the first page is filled with nonsense from third party sellers.
These are the reasons I use Amazon less and less. Stories about fraud (and more importantly, Amazon siding with a scammer for no good reason) just add more weight.
If fraud was a huge part of their business, they'd kill the 3rd party sellers from their platform, but I doubt it is. I think it's a net positive as a whole, but a small number of customers hate it. What they need to do now is improve those quirks you mentioned. That's much more reasonable then killing the whole marketplace.
Not saying fraud isn't an issue, and there's certainly room for Amazon to improve in that area and keep it at bay even more, but I think the reason they don't do what you say is probably that they k ow the numbers, if they see a million third party purchase, and only 1000 were fraud, its not really cause for killing the other 990000 sales.