> rationally should make as efficient use of the land as possible
These two statements are contradictory.
The value of the bare land (just pure dirt) is low no matter where it is.
But the second statement is where the consequences show up. The LVT idea isn't really to tax the bare land, it is to tax it as if it was being used by the most financially productive way possible.
So, tell me how is that not a tax that is based on something that doesn't actually exist today? The assessor can say: Sure, it's just bare dirt, worth nothing right now, but you could have a skyscraper there and if you did, it'd be worth a lot. So we'll pretend it's worth a lot and tax based on that.
The other bad consequence of LVT is that it's supposed to force every bit of land to the most financially productive use. Do you want to live in such a society? Something like a free playground is never the most income-generating use for a patch of land, but it's a wonderful thing to have in towns.