Right, this is the part people miss. The top wealthy aren't getting hundreds of millions of dollars per year via truckloads of cash which they then somehow pay a small tax rate on. Instead they (for example) own a large % of a company and when the value of the company goes up, the value of their wealth goes up. So in some sense that money is imaginary.
Imagine buying a million dollars worth of gold bars and putting them in your house. Next year, the value of gold has gone up 50% so the same pile of gold is now worth $1.5 million. So you've "made" $500k! But it's not a real $500k, it's an "imaginary" aka "unrealized" $500k. You might find it's not really worth that much if you attempted to sell it all. Until you've "realized" those gains buy selling your gold, you don't pay taxes on it. I think most people agree that's a reasonable policy, yet a lot of people are outraged that there is no "wealth tax" to force the gold owner to sell off gold every year to pay for any unrealized gains.
What people ought to be outraged at are the loopholes the wealthy exploit in order to not pay taxes on realized gains such as the "buy, borrow, die" loophole (https://wallethacks.com/buy-borrow-die-estate-planning-strat...). For example, wealthy people will take out huge loans backed by unrealized assets (stocks), use the loans to fund their lifestyle, and then die without paying back the loan. Then your heirs use the inherited money to pay off the loan at a way lower rate than normal because the stock cost-basis is stepped up at the time of inheritance.