Welcome to taxes. You could have had something, then the government says you can't and you have to live a different lifestyle. All the options here are morally gross and it is easy to justify either side.

If land values have truly doubled in 8 years it isn't like the family involved is out of pocket. They've made a small fortune. The idea they can make a small fortune and prevent land from being used is also morally gross. The only justification is that a large hurt is diffuse where the small hurt would be concentrated. That is a defensible philosophy but it is also one where eventually everyone is worse off. And it isn't like this is an erosion of property rights; they are being taxed on benefits that they are not responsible for creating. 1.5% land tax so people have to re-buy the land once a generation is as good an idea in tax law as any I've seen.

I agree that having to change a lifestyle because of taxation is pretty awful and the system should strive not to do it. But I've visited places like Hong Kong and seen the density of living there. We're talking an order of magnitude more people. The number of people who come out ahead from that sort of property development is so overwhelming we can't process it using intuition and positive stories about individuals.