Vast majority are realizing their gains as rent. A land tax would just be taxing those gains before they can be recycled into the real-estate market. Perfectly just in that case.

If you're talking about an individual not using the land commercially - well theoretically the tax burden lowers the sale price. You don't pay both. At 100% land tax, the sale price would be zero. You pay only as you use the land. That also seems just to me.

Well I have news for you… governments are coming for unrealized gains, they will not care if the money is on hand, they’ll fire sell your property if you don’t get a loan to pay the taxes. It’s a mathematical inevitability. And by that I mean governments are going broke and will try to find ever more creative ways to raise money, and unrealized gains, tax normalization, is one of the bigger leavers.