Too much responsibility, too fast, without proper training and preparation
Good, cool opportunities for innovation only come after the expected 60 hour/week of work
Consistently unreasonable expectations for project schedules, wouldn't take what I thought into consideration, this made each project extremely stressful
Facilities and budget for proper tools and equipment subpar
Lack of appreciation and respect for hard work, often the opposite (disappointment) if a project was slipping behind (the unreasonable) schedule. These projects were usually even more and harder work.
Unable to commit to any weekday evening plans due to long, sometimes unexpected hours (and sometimes working weekends too)
Low pay - didn't realize this until I moved on. My next employer offered me more than what I said for salary expectations (this happens?!), after warning me pay might be below market.
Most of these things I didn't fully understand until my next engineering position.