I agree that it's more "difficult" than "infeasible" so I've corrected above.
But I'm not sure I agree that the difficulty is due to being an oligarchy. In a democracy where the majority of citizens have the majority of their capital tied up in land (as is the case in the US and many capitalist democracies), shifting the tax burden onto land seems like it would be broadly unpopular.
I do agree with your main point though that a democratic society with a free market economy could work very differently, it's really the transition that would be broadly unpopular, and therefore politically difficult in a democracy.
But I'm not sure I agree that the difficulty is due to being an oligarchy. In a democracy where the majority of citizens have the majority of their capital tied up in land (as is the case in the US and many capitalist democracies), shifting the tax burden onto land seems like it would be broadly unpopular.
I do agree with your main point though that a democratic society with a free market economy could work very differently, it's really the transition that would be broadly unpopular, and therefore politically difficult in a democracy.