It's also, effectively, a promise to maintain Internet-wide routing table entries for every page on the web rather than every host (which is something we also can't really do today).
Multicast for everything is difficult. But would it be all that difficult to have 100k or 1M entries?
Something that would definitely be doable today is an IP header that stores 25 or 50 extra destination addresses. But it seems like nobody really cares. Just make streaming services send out a thousand packets with identical data.
Well, it could be done based on microtransactions. To set up your mcast tree you need to pay. The slots are auctioned off every X minutes on a DAG-chain-block-thing.
