Unfortunately I see a second problem with these decentralized marketplaces, and that is trust. Many people like it when they can rely on a centralized authority when something goes wrong with a trade. On OpenBazaar, there is the option to use an escrower (moderated payment), but if the escrower (moderator) fails in assess the situation correctly (e.g. if a vendor presents him fake proof about an item that was sent) or is untrustworthy, all they could do is to call the police - and depending on the good they purchased, or privacy reasons, they may not want to do that.

I read from a service from a business called OB1 who "verifies" OpenBazaar moderators. However, even totally trusted people can be fooled by good scammers. Thus, in reality what would be needed would be some kind of insurance for the escrowers, but this is currently (probably) unrealistic.

Thus I think there is a niche for e-bay like crypto marketplace websites like Bitify. A big problem however could be - depending on the country they operate - that these sites must register as a financial institution if they offer escrow, or limit themselves to provide means of communication.

PS: Just got an idea I may develop further: One of the problems of decentralized marketplaces seems to be the communication with the postal service, because it's difficult to prove a vendor didn't send the correct item. What about a crypto-friendly postal service which offers an option to verify the content of a shipment? Problem may be that such a service could be costly, but what I have in mind is that the vendor should pay an additional fee which he gets back if the buyer doesn't request dispute resolution ... Is for now a very immature idea, maybe it already exists.