Well then, don't bother with it. Limiting your skill set is always a good career move.
Hey now, I code for food. Just cause I think some system is crap doesn’t mean I am not the best at it. Admit the overhead in CPU cycles and memory are huge. It is lots easier to code though when other people did the actual thinking. I guess it is a trade off. Thought vs speed and efficiency, I prefer the programmer be good and his or her code be efficient and quick. No matter how smart or good the completely OO coder, their stuff runs slower than non OO stuff.
OO is good for large projects. Allows compartmentalizing thought and responsibilities, but given OS400 was written by a three or four man team, I mean big stuff.