That has to be the most regressive tax I’ve heard of in western Europe. Absolutely excessive and I’m sorry it’s happening to you.
Belgium has a home value tax as well, based on fictional rental income + a very convoluted calculation + different % surcharges per council. I find back that it’s on average about 700 to 800 euros per Flemish adult person, but it has large variations. It causes a lot of grumbling, but for most people it’s not considered excessive.