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.

I experienced VAT in Europe for some years and it is an overly complex sales tax. Simply have a sales tax which excludes uncooked food at grocery stores and excludes tax on some reasonably small amount of household energy each month. Then delete other taxes.