When you are in the right-hand seat, it is easy to bitch about captains you fly with. When you change seats, the job changes character:
As an F/O your priorities are to make smooth touchdowns, whereas as a captain, a greaser is not a priority, rather the "big picture" takes the front seat.
As an example, I flew back to homebase in ****ty weather. My F/O looks at the ETA in the box and says something like "I should be able to make the xx o'clock airport train". In contrast, in my mind I was already going through a missed approach followed by a diversion to another airfield, the consequences to passengers, whom to contact, etc, etc.
So you may think that you're a hotshot F/O, that you know how to fly the plane better than the skipper (sometimes you do) but things aren't quite as black or white as you might think.
As for DECs, do doctors apply for nurse's jobs?