> When asked what is his top priority, his manager responded with "Everything is a priority". Then I would work a bunch of overtime to find out it wasn't needed at all.

I've had bosses like this, and you quickly learn that you work the highest priority item and when a item slips past a deadline, nobody dies, nothing bad happens 99.99% of the time.

I've always emphasized "What is the best use of my time" throughout my career and giving me the "everything is a priority" line is a sure way to make me not care at all.