I think the prevalence of the "falsely shouting fire in theater" quote is a product of usage of that quote in an important freedom speech decision (that ultimately ruled against free speech).

Thomblake suggests convincingly that the quote was referencing a then recent disaster, but you are correct that the circumstances in theaters today are so different that the quote lacks the same impact as when it was written. In other words, the same legal reasoning today would probably be supported by a more culturally relevant example.

For what it is worth, the legal standard on liability for possible harm from speech is different (and more speech protective) than the decision in the Schenk case from which the quote originates.