The main concern is aptly summarized in the article itself
U.S. officials have expressed concerns that...Americans who’ve made windfalls betting on the market’s meteoric rise are evading taxes. Such worries have been a hindrance to the industry going mainstream, even as Wall Street increasingly embraces Bitcoin and other tokens amid a global investing frenzy.
So it is basically about all those "founders" of alternate coins, their supporters, US-based influencers etc. who have made millions in the bullrun by promoting Alt-coins. People are now making ludicrous amounts in meme-coins and the IRS is worried that it won't get the taxes.
To be frank though, what right does the US govt have on the gains of an individual who has found a way to gamble on these memecoins, put in a few thousand dollars and turn out to be the lucky sons of bitches for whom that amount goes from 10X-100X. Its not like this keeps happening in crypto. Only during the Alt-season, such things happen.
The cryptocurrencies have nothing to do with the government. An individual chooses to invest their own money at their own risk. What "right" does the IRS have to tax those gains?? Its not like they are providing the underlying infrastructure as in the case of taxes on corporate profits.