“most”? so you’re going to throw the dice with peoples lives on the line…
here’s the thing. the people who would meet shidduchim at mixed partes, are not being left at the alter. people are not remaining unmarried because, nebech, they missed mixed parties.
there aren’t more unmarried 40 year olds (frum) today then there was 30 years ago. and the shidduch crisis that does exist stems from the age gap, not lack of mixed social settings.
people are getting married. even those who dont go to mixed settings. think of it like this: there is NOT a larger pool of unmarried singles in the chareidi community (which eschews mixed settings) than in the MO community (which favors mixed settings). hence the chareidi folks are getting married in at least as much numbers as the MO folks – without the mixed parties.