Closing the markets would be the ultimate act of panic, and would guarantee a major recession.
That's true. But also this is just a correction, and not based on any earnings changes other than the directly impacted stocks like airlines which were cut in half. They can muddle through on loans.
OTOH the worst case is that the economy needs complete restructuring due to permanent changes, lots of fatalities, etc. I don't think that is likely at all, but the markets would be critical for obtaining the capital to restructure.
Closing the markets would be akin to FDR's economic interventions. Those caused 10 years of off and on depression instead of a much quicker recovery.