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.
It's Illinois. The state is a financial disaster. They are jacking property taxes because they don't know of any other way. Certainly spending less and rooting out the massive systemic corruption do not appear to be on the table.
It may be what property taxes are designed to do but the social agreement that allows them is that taxes are designed to raise funds, not force people out of their homes. The Romans tried this. They ended up with their citizen farmers walking off the land because of the taxes, and ended up going from some of the most advanced farmers to not being able to feed themselves.
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.