In my experience (or lack of
)...
Normally when starting at a regional airline, everyone there doesn't have any 121 experience. Everyone is NEW. Some may have more hours, or more instrument approaches, or more dual given. But in terms of flying passengers on the line, everyone is on the same page. Since everyone is inexperienced then, the difference between those successful in the long-term versus those who fail is recognizing the lack of experience. I know when I got hired with my first company, I knew a lot about the airplane systems-wise already. But otherwise I didn't know squat. Even after 1000 hrs of 121 turbine time, I still am learning a LOT every day. I'm still inexperienced to a large degree.
The day you believe you are experienced and know it all, is the day you fail. Because you never know it all, and you always have something to learn.
ASIDE:
To be honest, I think of instructing as a much more important job than an airline pilot will ever be. Why? Because you are developing the rudementary skills which will carry a pilot through their career. These basic skills are the flying skills they will use when flying 200+ people around the world someday. Remember the law of primacy? I know that I still remember (and use) knowledge and skills I learned at U of I in my every day work. If my instructors had not done their job from the beginning, teaching me to FLY (not be a systems operator), they would have done my career a huge disservice.
Even though I didn't instruct much, I'm still big on it. I honestly believe instructing is treated improperly by the ENTIRE industry.