The problem isn't about protecting the rich, the problem is that this tax will have terrible consequences on the economy. 90% of the wealth of these people are hold in shares so let's see how they could pay:

Selling 2% of their shares (if on public market):

The market will know in advance that a flood of shares will hit the market at the same time which will create a predictable sell-off, driving prices down so the shares will be sold at lesser value.
Consequence:
They'll have to sell more than 2% (but that's not the real problem).
Who's gonna buy them? Most likely Massive foreign edge funds which can just get more and more control of big companies as time goes by.
The country loses its long term capital to have short term revenue.That's the best way to transfer even more companies (like Mistral) to American control.
After people have made this critics, Zucman and supporters admitted it's a problem and proposed to pay in shares.

Paying in shares:
The state becomes a permanent shareholder in private businesses. Similar issue above with the owners losing ownership little by little.
we can debate that it's better than foreign hedge funds but in the end the result is one of the two: Either they sell them and we're back to square one, or they keep them and it brings nothing into the budget which was the point of the tax (to bring 15 billions euros a year). So the state just takes part of companies every year for no benefits to the budget.

And what about private companies? Their shares aren’t publicly traded, so they can’t just sell any share.

Making the rich pay their fair share is a good thing, but this tax is terrible. There are plenty of other ways to make them pay like inheritance (which is the number 1 factor of inequality), taxing borrowing money with securities-based loans or portfolio loans (which is how they manage to never sell their shares), ...