There are tons of people (actual serious people, not like SBF) working in this space and building these things now, so they are definitely more than theoretical, but they are not at the mass adoption stage.
And no offense, but this response has echoes of people saying federation would never work. But it’s just a different utility to accomplish similar goals to centralized forums. And when the old-fashioned, centralized alternatives really start to self-destruct because of their inherent flaws, the merits of the decentralized version become more obvious.
I’m actually pretty shocked that Lemmy/the Fediverse beats the same tired old drums about NFTs (ape jpegs being the most obvious), since they are red herring arguments. A tokenized jpeg has no value because a jpeg has no value. A tokenized security has the value of the underlying security. The token is just there to eliminate the need for accountants since the open ledger shows its work and the entire chain of custody.