Tornado Cash's contract is still up and running, that's where the decentralization comes from. You could claim that it's too hard to run your own Ethereum node (for the RPC access) and host your own copy of their frontend, but this is still possible.
I agree that contract is still up and running, but of what use is it if an average Joe can not access the platform to mix his Ether?
Where is the said contract going to get volumes of ETH so that it's possible to obfuscate them and thus make it a fully functional decentralized mixer that anyone can access?
IMO, I believe decentralization becomes more meaningful when it involves masses as well, just like what we are seeing with Bitcoin right now
