Most of the wealth held by the rich isn't money failing to circulate. It's productive capacity producing goods for others. Elon Musk's wealth isn't a vault full of gold coins. It's a factory producing cars that other people get to drive.

Piketty's book describes this phenomenon as well - his book is fundamentally about the world moving from a situation of having a $1M factory producing $100k in income to a situation of a $2M factory producing $150k in income. (I.e., r=2, g=1.5.)

I tend to rely ( probably too much ) on Adam Smith for my ideas about capitalism, and so far as they go these phenomena are not that.

Specifically land leads to Ricardian rents, and historical examples of taxing land rents abound. Japan went from medeviel backwater to industrial giant in ... decades through the use of land taxation.

At some point, they decided the classical Japanese values were more important and that is when the industrialists took over as an update to the Samurai and the rest is history. I don't blame them - classical/medieval Japanese culture is extraordinarily beautiful. But the Bushido Code does not mix with machine guns.

Generally, capitalism if practiced by ... Vulcans or robots would not result in most of what we attribute to it as ills. But humans love to cheat, and the cost of prosecuting all that cheating is probably too high.

We also seem unable to develop a media culture that does not fawn all over the rich and powerful.

Actual Capitalist ethics emphasize consumer surplus most of all. Whether the externalities are what we think they are is a much richer discussion. Quite difficult. It is important to realistically believe you are serving your fellow man in this way.

I don't think history has proven Das Kapital to be complete bunk - it's kind of like Freud - often said to be bunk but many of his ideas were revolutionary at the time and are considered to be mostly mainstream now. Things like the subconcious, ego, the importance of childhood development on adult psyche - even if not completely scientifically rigorous are useful tools for understanding our reality. But it was his more loony ideas that stick out now and for which he is remembered. So that's why people think that firstly rather than take note of the other stuff.

And so it goes with Marx, the first volume certainly is hugely prescient and correctly predicts much of the economic progress that has come since. Workers as stakeholders in a business is considered fairly mainstream in many modern economies as is the role of the state.

But as with Freud it was the later stuff particularly in Volume 2 that got him his reputation as a looney. Sadly he formulated the manifesto as a precursor to writing the book and this bound him to a particular conclusion even if his research in the meantime didn't match up. Volume 2 was never finished and what was eventually published was the unfinished manuscript as well as some notes, post humous.

It is unfortunate that Marx couldn't have just left it at Volume 1, and put aside the fanatical fervour of his younger years. Had he done so it could have formed the basis of a more humane society and he would not have been associated with some of the more attrocious implementations of communism, and a reputation which he doesn't wholly deserve.