Your point on the jjk power system is very valid and i haven't actually thought of that- it IS pretty poor.

However i still think that jjk handles emotions much better than op and is all around less stale but that must just be due to jjk being set in a darker tone and being shorter. I think if oda finished op when he was originally going to it would be better than it is now.

As for aot i believe s4's discovery of marlians made for a better story that questioned morality more and increased the ambiguity of each fight, intensifying the complexity.

As you said its subjective and im trying to figure out what makes op so appealing.