There are market places that you can pay bitcoin or crypto with. They do not accept it directly though, they usually handle it through a third party payment processor much like bitpay works.
It would not be legal and more of a black market kinda thing. The government would probably scrutinize the shit out of it.
Your vision is good and indeed it might be the future but man bitcoin has a long, long way to go before there can be sites like these. It could be a thing in niche crypto markets where its legal though.
By the way, you can buy gift cards kinda stuff via Bitcoin.
You already get legal markets you can spend bitcoin on -_- There are many things you can buy with bitcoins.
First of all, a "crypto Ebay" would not be feeless. Handling with Bitcoin costs always fees.
Secondly, crypto Ebay's already exist in the Dark Web. There you can find many marketplaces and Ebay clones where you can buy all things and stuff (legal and illegal) with Bitcoin and cryptos like Monero.
Maybe OP didn't know about it or had forgotten about how crypto became famous in the dark web for something like that,
And we still carry it till this day because some still see's crypto or Bitcoin only as a money for illegal activities because it was once known for that purpose.
99.9999% of crime is done using fiat.