Besides, many of the best tax evasion strategies are legal -- you just need an army of lawyers and a large pile of cash to deploy them.
Isn't the premise of the linked paper that the wealthy use these foreign banks to avoid getting caught underreporting their income and assets? That's not legal.
Your average middle class person can't afford to risk taking the irs to court.
consequentially the German IRS has bought data from Swiss and Liechtenstein tax haven whistleblowers. several times so. and to the amazement and applause of the public, very prominent figures went to jail. like soccer legend Uli Hoeneß.
the corresponding Wikipedia article is surprisingly not available in English yet:
https://de.m.wikipedia.org/wiki/Steuers%C3%BCnder-CD
long story short: if you, the American people, elect representatives who want a fair system, you will get a fair system.
of course IRS will go after tax fraud at scale if you make them do that.