Mainly work culture. The union protects everyone, which can be nice for job security, but they will also actively protect employees who are bullying others and not doing their job. If you go to management instead about issues like this, the union actively works against management and prevents them from doing anything about this. Some coworkers are cool, but overall some of the coworkers that they keep around make the job miserable. Generally anyone who is worthwhile and nice to work with will not stick around for long. There is no incentive to do a good job here, you'll be actively picked on and taken advantage of by others.
Ability to climb in this position is also difficult. There is no way to get pay raises for doing a good job, it's just solely based on what the union decides and does not matter if you work hard or are on your phone half of the shift. If you push for it and bug management, you could potentially work into a driving role, which can pay well if you want to work long hours. Working up into management relies on someone else moving out, which is totally out of your control.
I rated work life balance low since these negative aspects of the job make it pretty draining, which definitely affected my non-work life negatively.
