First, let me say I do think I interpreted that article's data incorrectly as the US at .81 Gini coeficient, when in reality its probably closer to ~.45. Medieval Europe was closer to 40, but definitely not the magnitude I took from my initial source.
There are several ways to look at inequality. The most simplistic way to so do is looking at relative wealthy by decile and comparing the ratio between the top and bottom. In feudal society, everybody was relatively poor, and the wealth gap may be on the order of 10-100X. In modern times, that ratio may be far larger and under a certain definition that would be mean higher inequality. I'll concede that this approach fails to capture the practical experience of the haves and have-nots over time, and having our's hit all-time highs isn't immoral if there is some baseline of sufficiency at the bottom. It also doesn't account for social mobility, which we exceptional at.
Still, we live in a novel time where orders of magnitude of wealth that haven't existed before. It is hard to fathom, and calls into question what is and isn't a de-facto privilege of enjoying.
Not commenting on the rest, just wanted to say something about you claim that "our" (I assume you mean US) mobilty is exceptional. That is an often repeated myth, and in fact part of the US "folklore" ("rags to riches").
Interesting, thanks for sharing. You're right about the folklore, and while there are some strong outliers that have done quite well in the US, but those would be hard to attribute to anything special about US education and support systems.
Although the ranking is named "social mobility" it isn't clear that that is what is measured; the report seems slightly confused.
The visual capitalist provides a definition of social mobility - children having a better life than their parents or being unconstrained by their socio-economic status. But the index they reference doesn't measure that. It measures more general Quality of Life metrics like prevalence of malnourishment or quality of the social safety net.
So while a high score reflects an easier life for the low end of the social ladder it doesn't actually measure their ability to move up it. I could on paper come up with a country that scored quite well on most of the index measures and had a rigid caste system where children could never outperform their parents and cannot escape their birth status.
There are several ways to look at inequality. The most simplistic way to so do is looking at relative wealthy by decile and comparing the ratio between the top and bottom. In feudal society, everybody was relatively poor, and the wealth gap may be on the order of 10-100X. In modern times, that ratio may be far larger and under a certain definition that would be mean higher inequality. I'll concede that this approach fails to capture the practical experience of the haves and have-nots over time, and having our's hit all-time highs isn't immoral if there is some baseline of sufficiency at the bottom. It also doesn't account for social mobility, which we exceptional at.
Still, we live in a novel time where orders of magnitude of wealth that haven't existed before. It is hard to fathom, and calls into question what is and isn't a de-facto privilege of enjoying.
I found this article which offers some more nuanced approaches to measuring inequality in different societies than Gini. https://mpra.ub.uni-muenchen.de/5388/1/MPRA_paper_5388.pdf