A more generous response would respond to the original point. If we tax the rural aristocracy (i.e. concentrated land-owners) out of existence, then who will then administer that property? The obvious answer is large-scale agribusiness which achieves mortmain and never dies. Given the history of the unholy alliance between ADM, Monstanto, and the US government, it is fair to ask if that would be an improvement.
Personally, I think unlocking the land from the trust-fund people cosplaying farmers until they can turn it into housing would be a good thing. But there are a lot of moving parts.
If not the aristocrats, then who? Someone will run things, and it isn't always obvious who will do it better.