There are three reasons to go back to school:
- You want to change careers and need to get new credentials to start that process
- You need additional credentials in your current field to advance your career further
- You have the spare time and money and want to learn about something that interests you
In the former two cases, you already know what new career you want and can work from there to determine what kind of additional education you'll need to get. In the latter case, you already know what you want to learn about and it doesn't matter what kind of value you'll get out of it. Neither supports "Maybe I should do something STEM instead of what I want to do," which tells me you haven't actually figured out what your reason for going back to school is. Given the cost, that's something you should be figuring out before you make any decisions.