I'm assuming by wealth tax you mean some sort of magical system where Zuckerberg is forced to pay off your student loans. However what will actually happen is the wholesale liquidation of the middle class to fill the twin bottomless pits of medicare and social security, while the billionares skip the country and/or hide behind arcane tax rules, and the Valley they leave behind gets turned into a jobs program for the homeless.
The other fundamental problem with giving a big additional slice of the national wealth to the poor is that they will spend it on consumer services (not goods, which are cheap), for which they have great pent-up demand. And then it'll be gone. At which point you no longer have a middle class to extract from.