Over the last 50 years this has been terrible advice on balance.
With more nuance it makes sense - avoid bad debt for lifestyle that doesn't produce future economic value, and avoid an excess of investment debt but carry enough investment debt in well considered assets that you can be part of our economic systems growth which is built into our society by design and enforced by our government systems.
Your advice is great for fairly financially savvy individuals, but most of us are not especially financially savvy. For the vast majority of people simple, albeit less than perfect, advice is much better than really good, but complex, advice.
With more nuance it makes sense - avoid bad debt for lifestyle that doesn't produce future economic value, and avoid an excess of investment debt but carry enough investment debt in well considered assets that you can be part of our economic systems growth which is built into our society by design and enforced by our government systems.