If you look at the effective inheritance tax rate (ie tax paid on actual money flow from dead people to inheritors), even the top 0.1% of all inheritance is around a 10% rate. See figure 2 in https://www.cae-eco.fr/staticfiles/pdf/cae-note069s.pdf. Note the the nominal tax rate is around 30% - the difference is because a lot of stuff is not taxed, or partially taxed.

I think the issue is that French inheritance taxation has both a very high facial rate and massive amounts of exemptions / loopholes. People that think they can grok the fiscal system in a few minutes look at the high nominal rates , not the loopholes.