A dissatisfaction with one's work that manifests as some sort of "what I do doesn't have meaning" or "what I do doesn't help anyone" is usually just an "I don't do anything relevant in my spare time" that is looked at through the wrong lens.
In a capitalist society, one should not rely on the same activity for both sustenance and psychological well-being or fulfilment. As many have pointed out before me, here and elsewhere, any hobby or similar activity stops being enjoyable once it becomes your job, i.e. once you pay your bills with it.
Instead of trying to stretch our daily jobs to fit two different goals, I believe we should, in fact, shrink our jobs so that they leave enough space for different activities that try to tackle the lack of meaning or passion in our lives: volunteering, cooking, making of art or just simply being there for our loved ones.
In other words, instead of the "equate life worth to career, find out life has no meaning, change career, equate life worth to new career" cycle, try the "equate life worth to... well, life itself" for once.