It is perhaps the singularly worst piece of financial advice ever provided on any forum anywhere.

Debt is only useful in acquiring financial assets with positive cashflow in excess of the cost of debt. The most common asset class this applies to is real estate, both commercial and residential, but it also applies to other productive assets.

Borrowing money to acquire speculative assets is a fool's game. It works great while prices appreciate, but debt becomes an unmitigated disaster when prices fall.

Further, failing to sell assets and realize profits is something professional investors simple do not do. Eventually, every asset class experiences a bear market, and building a pyramid scheme of debt to buy volatile assets will inevitably lead to a complete wipe out.