There is nothing wrong with having an umbrella term like “STEM”, “liberal arts”, “humanities”, or similar. The problem comes in how the umbrella term is used. Sometimes “STEM majors” seems to be used as a general catch all for almost anything desirable about major selection. To the point of this thread, saying STEM majors have good job prospects is an example of this. Some STEM majors are associated with a higher salary or high job demand. Other STEM majors are associated with lower salaries and less job demand.
Some example numbers from the Berkeley survey at https://career.berkeley.edu/survey/survey are below. I am defining unemployed as (% Seeking Employment / % Not in Grad School). Some STEM majors had high starting salaries of $116k+ with low unemployment, while others had starting salaries of under $50k with more than 1/3 unemployed (with only BS), which is similar numbers to theater and other not-in-demand non-STEM fields.
Better Job Prospects
CS: Median Salary = $116k + $20k bonus, 8% Unemployed, Common title = SW Eng
EE & CS : Median Salary = $117k + $20k bonus, 12% Unemployed, Common title = SW Eng
Overall Average Across All Majors (Both STEM and Non-STEM)
Median Salary = $73k, 26% Unemployed
Worse Job Prospects
Env. Sciences: Median Salary = $42k , 35% Unemployed, Common title = Research Assist.
MCB: Biochem: Median Salary = $45k, 38% Unemployed, Common title = Research Assist.
Theater: Median Salary = $44k, 35% Unemployed, Common title = Actor