The milestone, though occasionally achieved by plays and musical revivals, is an increasingly rare one for new musicals, which have historically been central to Broadway’s artistic and economic life but have struggled mightily since the coronavirus pandemic. Only three other new musicals that opened in the last six years — “Six,” “MJ” and “& Juliet” — have become profitable; the Bobby Darin musical “Just in Time” is likely to be the next one to get there.