That's obviously not ideal for your family, but it's precisely what property taxes (or more directly a land value tax) is designed to do. If your grandparents couldn't use the land in a way that covered the property taxes, then the argument is that the use of the land is likely inefficient and it would be better overall if the land was being used more productively. It sounds like the system did exactly what it was supposed to do.

Edit: not to mention that VAT and sales taxes are considered regressive taxes that disproportionately burden the less wealthy. I would much quicker remove VAT than property taxes.