A ROTH IRA is designed so you pay taxes up front and _never again_. This is the whole point. It is easily available in the USA, I even have one. Peter Thiel used a self directed ROTH IRA to make a ton of money. He will never have to pay taxes on that, because it’s in a ROTH IRA. This is not a tax loophole.
He _may_ have engaged in insider trading or something, in order to make so much money in the Roth. That should be protected, but is really not related to the fact that he used a Roth.
They missed that a Roth IRA needs to be a self-directed IRA to invest as Thiel does, most people don't know this and invest in ETFs or mutual funds giving meager returns. And, you need to have a high net worth to invest in private stock, especially in the formation, pre-IPO, stages of a company, and a high net worth reputation to have venture capital credibility.
Also, the main reason that Roth IRAs passed in Congress is that greedy politicians, on both sides of the aisle, want that tax money upfront instead of waiting decades to collect.
There should never be an argument that the government is some steward of our money and that the insane amount of money they collect from us is somehow wisely spent as our fiduciary.
He _may_ have engaged in insider trading or something, in order to make so much money in the Roth. That should be protected, but is really not related to the fact that he used a Roth.