I am currently a freight stock picker. The job is great if you are able to keep to yourself and keep and smile on in front of management. The pay, for what the job entails, is very good. If you enjoy being able to keep interactions to a minimum and focus on your work, then it is a great job.
You are merely. Not your employee number, but your productivity and accuracy for that day. It does not matter if you are able to exceed numbers on a daily basis. If you have one bad day, or one error outside of your control, then that is all you become to your management. The old adage of "what have you done for me lately," is very apt here. Any sense of identity and individuality is thrown out of the window here. You must conform to their set of standards otherwise you are seen as a problem.
Lack of career advancement is non-existent, unless you assimilate. From my experience, you have to excel above and beyond all goals in place to be even considered. Only then THEY will place you where they like. If you request to learn other responsibilities, then it becomes a constant barrage of misleading or leading on. There were many empty promises made that lead to nowhere.
It is a good job if you are able to fit their mold, but disagree or speak your voice on any issue, you become a nuisance.
All that is required of you is to keep your head down and focus on the task at hand and you can excel here. It could be an excellent career if not for the management. Otherwise, it's just a decent job that brings home the paychecks.