For instant exchange that you can use with Tor, you can use https://exch.cx/
You have a misconception about what is decentralization. The service you mention has nothing decentralized. It's just an accountless exchange swap.
Lot of people don't understand this concept. That's why we were reading people calling Localbitcoins a decentralized platform.
Decentralization or decentralisation is the process by which the activities of an organization, particularly those regarding planning and decision-making, are distributed or delegated away from a central, authoritative location or group and given to smaller factions within it.
It's not a decentralized exchange either