What are some good (career-wise, so not overhyped but not dying either) STEM fields for CS graduates to pivot into?
Your question assumes the individual is not sufficiently strong or motivated in CS, and is more disposed to another STEM discipline. How can anyone answer your question?
Computer Science is a STEM career that typically supports other non-computer science STEM areas.
So, taking additional classes/certifications in field/area would like to pursue post graduation is helpful. aka biology classes for computational genomics.
Computational genomics, data science and computer security are pretty good long term prospects. A few computer science graduates areas of concentration also include database related issues (big data, administration, etc), systems analysts,network architects.