Possibly the easiest way to think about STEM is to push aside the grouping altogether and think about each major individually. In reality, tech and engineering have better job prospects than math and science. However, tech is in the midst of a boom that might turn out to be nothing more than a bubble, and Engineering has a reputation for being on the dull and corporate side.
In addition to that, there is much more fluidity in the value of a major than there used to be. Employers are more interested in skills and knowledge than the name of your major, and your school pedigree matters too. That means you should think of your major as a choice to pursue a particular skillset, and recognize that some or most of that skillset might be present in other majors too.
If you are genuinely interested in some part of STEM, then you should be excited to learn, but keep in the back of your mind the prospect that you may need to work in finance or health care as a backup plan. That will pay you reasonably well but might not be what got you into the field. On the other hand, if you are trying to get into STEM purely for the job prospects, then face the fact that you might have trouble maintaining interest in the day to day work, as well as the possibility that the job you were expecting might not be there when you graduate.
The final decision is yours, but you should balance practicality with passion. Don't select STEM just because you think it will get you a good job, but also don't choose it without thinking about the job market at all. While STEM has a lot of promise, things can change quickly in the years you are in school.