Read the Room
You can learn a lot about a potential job based on how current employees feel about it. If everyone seems really happy and excited for you to be there, you can expect a generally healthy workplace and strong comradery. However, if the employees don’t even pretend not to be miserable, it probably won’t be a great situation.
This person discovered that on their first day on the job. Everyone was absolutely miserable. And on top of that, the company didn’t even bother to provide any actual training. Imagine hating a job that you aren’t even sure you’re doing right… It’s no surprise that they didn’t even make it through their first day.