It’s not at all time highs. Your chart combines the data for both genders, which causes the decline in employment to be masked by the separate trend of women working outside the home. Male prime age employment is down 10 percentage points from 1955:
https://fred.stlouisfed.org/series/LRAC25MAUSM156SMale 20-24 employment rate is down 14 percentage points since 1960: https://ycharts.com/indicators/us_labor_force_participation_...