Besides "sounds cool with shock value online"
A real GDP decline of over 10% year over year for more than 1 year is the biggest signal. Ofc, I noticed the US Federal Government has been cooking the books since at least H. W. Bush (maybe longer) by including tech stock potential gains as part of GDP. Take out tech stocks, the US economy looks like it will to historians.
Even in the modern day, an economic depression is associated with massive unemployment, deflation, reductions in the trifecta of industrial output + consumer spending + international trade, with the final kicker being reduced credit availability. Currently, interest rates are relatively high (historically middling) which has effectively restricted consumer credit, while the national credit rating has fallen.