Payroll tax is more akin to a government pension program in that your payment roll gets you money back when you retire. Counting as just another tax really cuts against years of government arguments to the contrary.

Family of 4 (2 kids under 16) in 2020 taking standard deduction, no childcare expenses, no tax deferred savings.

FICA Payroll taxes paid 50k * .0765 = 3825

Tax Burden 50k - 24800 (Standard deduction MFJ) = 25600

25600 = $2676.90 in FIT taxes owed before credits

Child tax credit $4000 EITC ~$750

Total Credits $4750

Total Federal tax burden -4750 + 3825 + 2677 = 1752/50000 = 3.5%

So not zero, but pretty darn close.