The crux of this issue, why everyone has something to say about it: is because the word 'comfortably' seems open to interpretation. But it's defined in a way that makes sense here.
For the purposes of the referenced study https://smartasset.com/data-studies/salary-needed-live-comfortably-2024, they used the MIT Living Wage Calculator https://livingwage.mit.edu/ and extrapolated out total compensation needed to maintain the 50/30/20 rule, where 50% of your total income goes to necessities, 30% to entertainment and wants, and 20% to investments or debt payments.
So it's really not up for debate unless you'd like to argue against the figures presented in the MIT Living Wage calculator or the 50/30/20 'rule'.