it's unpopular because IRS only goes after low-level tax cheats, not the already-rich ones who steal far more, and funding them more doesn't change that priority. similar to police.
In this particular case, this funding does change that priority. Janet Yellen has instructed that "any additional resources—including any new personnel or auditors that are hired—shall not be used to increase the share of small business or households below the $400,000 threshold that are audited relative to historical levels" [1]. Unfortunately, auditing extremely wealthy individuals is complicated and expensive because you're pitting underpaid and overworked IRS employees against a wildly complicated tax system that is exploited to the max by the super-rich and their well-remunerated tax lawyers.
https://www.irs.gov/newsroom/irs-announces-sweeping-effort-t... (“IRS announces sweeping effort to restore fairness to tax system with Inflation Reduction Act funding; new compliance efforts focused on increasing scrutiny on high-income, partnerships, corporations and promoters abusing tax rules on the books”)
[1] https://home.treasury.gov/news/press-releases/jy0918