For me it's teaching. I did some substituting last school year for the same district that I grew up attending. (Lame, I know). This is a relatively large district in an upper upper middle class community and still has so many staffing issues. On an average day it was common to have 50 vacancies needing to be filled just at the high school level. At worst some days would be over 100 assignments for subs to fill in at the high schools.
Not to mention with the onslaught of new technologies, it's a losing battle to try to get the attention of these kids. I totally feel that technology can be used to great benefit for learning. But all I've personally witnessed is that in reality technology (mostly phones and school provided laptops) is used by students as a distraction and difficult to regulate how it is being used. I also feel that it has strongly affected the quality of the content they are meant to learn.
I haven't even touched on low pay, fear of backlash teachers face for teaching little Johnny that the Civil War was fought over slavery and not disguise it as states' rights, and general underappreciation and BS from unruly students.
In short I've learned I will never ever be a full time teacher.
So please let me know what other industries are sinking ships to be avoided.