Decentralization is not a human nature. By creating a decentralized marketplace, you are trying to bring anarchy in social animals, it doesn't work that way because humans, i.e. social animals, always try to team up, group together and centralize the power. Over time, that will happen to decentralized marketplace.
If it's not for average users and only for crypto-enthusiasts, then it will still be very hard to keep it alive. Number of crypto enthusiasts is low, the number of those who are paranoid about their privacy, is super low. If number of your customers will be super low, then there won't be enough goods placed on your decentralized marketplace, so it will eventually die and people will be forced to use eBay & Amazon.
Also, I don't get it, why are some people so paranoid about their privacy? I sometimes think that some people work online and never go out to protect their privacy or if they go out, they were hoodie and dark sunglasses. Doesn't make sense.
I understand your point of view. But i still think such a market would be interesting for a lot of people.
Lot of online industries are now heading toward decentralization architecture, and i don't think e-commerce will be an exception.
Decentralization offers so much benefits ( even if you don't seem interested by it ) such as privacy, server downtime and censorship resistance, increased accessibility... that i don't think the old, simple client/server infrastructure will still be relevant in 10 years.
I may be wrong tho, your feedback is appreciated.