This is the law functioning as intended. Thiel's case is a one-in-100-million+ event. He may have the only Roth IRA in existence that's valued at over $5 billion. But he didn't do it by exploiting some sort of "loophole" or paying high-priced accountants to shield his assets in foreign entities offshore. He put his investments in a Roth IRA just like any of you can do. The only difference is his investments were in the top 0.0001% in terms of performance. That's generally how people get to be billionaires.
And that's not even to mention that the assets in a Roth IRA are essentially worthless to him - he's not old enough to make withdrawals or take distributions tax-free and you can't borrow against a Roth IRA. The funds are essentially unavailable to him for years to come unless he wants to pay taxes and penalties.
Again - this isn't a tax dodge. This is someone who used the law exactly as intended without any illegal or shady dealings and happened to be incredibly fortunate.
The whole article is a hit piece designed to get whip people into a furor. And lately I've been noticing propublica publishing a lot of those.