I’m sure that many members here are, like myself, old enough to remember (even back to pre-VII) when Sunday night Mass in the US was routine. It fell into use when the vigil or anticipatory Mass was introduced, and that is a relatively recent innovation (the last 30 years or less).
If I were voting in that parish, I would say forget about these night Masses completely (with the obvious exception of Holy Thursday, the Easter Vigil, and Midnight Mass at Christmas) and get your butt into Mass on Sunday morning, which is the traditional and intended time for the major parish Mass of the week. Christ didn’t rise on Saturday or Sunday night. The reason all those “young adults” are showing up on Sunday night is that they are sleeping off their partying in the morning, which is no excuse for missing Mass.