So far I've yet to see a convincing argument for what "Web 3" is and can offer that we can't currently do without the use of a Blockchain. It all seems to boil down to "it'll cost something to do something", which isn't exactly a convincing argument on its own. The responses to this story read rather like Facebook comments on controversial news articles - there's a bunch of comments claiming the website is a bunch of…
Instead of going through offshoots trying to find the killer app, I'd much prefer to see cryptocurrency tech evolve in order to bring costs down. Take the base use case of keeping "bank account" records and run with it until it works (as of now, it does not). Out of the viable -- for my definition of viable -- cryptocurrencies out there, the only one I see moving in the right direction is Ethereum. They are taking their sweet time, though.
If a killer use case is needed, think micropayments: The ability to pay 0.1¢ to listen to a song, paying directly to the artist.