The new forms are typically more than non-financial folks can understand.  I'm with garman on that one, I don't expect my plumber to understand how income taxes work.  Folks who learned under the "old" system that they could save money for vacation by claiming S-0 now have no way to enter withholding allowances.  If you follow the directions in the new (and "improved"?) W-4 you should end up with $0 balance due/refund at the end of the year.  But nobody reads the directions, and most people don't want to end up at $0 when they've come to rely on big refunds to pay for stuff.  If it's not in a 15-second Tiktok video, they can't be bothered with it.  So you end up with Taxpayer filling out the W-4 as married with 2 CTCs, then Spouse gets a new job and fills out a W-4 as married with 2 CTCs, and suddenly they owe thousands of dollars at the end of the year.

Another thing I run into that I'm trying to get ahead of is when CTCs age-out folks really should fill out a new W-4.  But CTC was a moving target last year with the CTC advances and phase-outs.  An extension for that insanity was in BBB that didn't pass and it still gets plugged into other legislation.  So who knows when/if that change will come and then whether or not the IRS will adjust the W-4 math to compensate for folks "double dipping" on getting CTC as an advance AND as part of their paycheck.

So yes, it's a mess out there, but I don't blame taxpayers for it.