Low inheritance taxes are actually a great predictor for maintaining social inequality over generations. If you wanted to reduce social inequality you'd instead want to drastically lower VAT (which disproportionately affects poorer people), adjust income taxes to lower the tax burden on lower incomes and raise it on higher incomes, and drastically raise taxes on income from capital (rather than labor). This isn't even simply an opinion, this is scientific consensus.
If you think the "wealth of a nation" is measured by the luxury of a few rather than the poverty of the many, you might as well just revert to feudalism.
Do you have one for mean income to upper class by chance? Even +1 Std Deviation move would be significant in terms of wealth building.
This is not true. Several of the highest taxed countries in Europe also have the best social mobility in the OECD: https://www.oecd.org/els/soc/1-5%20generations.png
It might be the case that Germany is particularly rigid, but that is not transferable to most of Europe and certainly can't be attributed to taxes.