You built a house on someone else's land, and then they tore it down. Build a house on your own land, as small as that land may be. From there you can create roads, bridges, tunnels to other people's land. On the web land is infinite. You can make your own land.
Also I think the analogy is pretty solid because it clearly illustrates the emergent benefits of being on a large centralized platform rather than a random URL. Land might be infinite but attention and clicks are not.
Farmers don't typically rely on a single farmer's market to sell their product, they participate in many markets, sell wholesale, sell from their farm, and might also have a direct-to-consumer option where they can ship beyond their locality.
Create once, publish everywhere — your land is the canonical source. Markets are for distribution.
Also, many creators already are publishing “everywhere”. YouTube is simply the most profitable. If YouTube income goes away, that ends the business, whether or not it can technically be found elsewhere.
In this analogy, there is only one farmer's market that anyone shows up to. In the real world many farmers may have alternatives, but that is a product of an entire industry spending centuries collectively cultivating those multiple distribution channels.