From a NW perspective it's better to invest in retirement savings that typically (and certainly have over the past 12 years) earn more than the interest rate on whatever debt.

Reliability of income is key. If you're in an industry/position that is more susceptible to job/income loss, that makes debt reduction more valuable. If you're in an industry/position where there is very little chance of losing your job or having a reduction income...invest away. Higher returns and the tax code is made to encourage investment (and mortgage debt).

I think most of the chatter in those posts were lifestyle inflation which is neither debt reduction nor retirement savings.