I think their societal structures are much better suited for the technologically advanced world we live in today.
Also, those are all very homogenous cultures. I don't think you can map what works there onto a very large, very diverse place like the US.
Yes, those of us in software can just be smart and work hard and be successful, but millions of others will not be, and it will be harder for them to get to where we've gotten to. Telling them to suck it up and "work harder" is exactly how you get wealth distribution, in fact. On terms you really won't like, just ask the Romanovs.
Millenials are the first generation in a long time to be worse off than their parents, and no, it's not because of avocado toast or iphones alone.
The "temporarily embarrassed millionaire" rhetoric is indeed meant to frighten, but your "anyone can make it if they work hard" is so mid-to-late-20th century Reagan-era rose-colored-glasses adorable, it's positively quaint. Let's just ignore automation and globalization and supply outstripping demand and tell those lazy kids to just get a job, eh?
Everytime I see this proposal it's of the "burning bridges" type. To ensure that everyone starts at the same crappy starting position. There are never any considerations what to actually use the tax revenue on. It's only intended purpose is to take away money from the "evil" rich parents. The justification is that the income is unearned but the flaw with this type of justification is that the parents clearly earned the money and paid taxes on it.
So far I haven't seen any proposals to redistribute the money to actually decrease inequality other than by making everyone equally poor. How about distributing that money back either in form of a UBI or some kind of trust fund that children can withdraw from at the age of 18. I haven't seen anything like that and therefore I'm against a 100% inheritance tax.