Whenever we try to compare players without using "metrics" there are a ton of "moving parts" anyways. Yes, TGeddy hit more HRs than Runnels. We include fielding, base running, OBP, and other stats that may be easier to understand, but hard to weigh in order of importance. We have to more or less wing it by looking at numerous stats to decide who we think is a bigger plus overall.
WAR tries to do all that and put it all into one number. Of course, it's flawed, but so are we, when we try to juggle all the stats to compare players.
The people who created WAR used a lot of science and data to determine how much each aspect of the game contributes to runs created (offense) or saved (defense). Personally, I don't need to have to understand every algorithm and computation to trust that they probably do a better job than I do at pulling everything together into one determination.
To me, the defensive input is probably the hardest for casual fans to factor into overall value. If you don't use defensive metrics, what do you use? Eye test on players you barely see play? Fielding percentage? Then, how much more valuable is it to be the best fielding SS in MLB vs the best fielding 1Bman? What weight do we assign to positional value?
WAR is not perfect. OPS is not perfect, but no singular stat or metric tells the whole story. WAR probably comes the closest.
To me, OPS does a pretty good job at showing all around batting value- it's better than BA alone, OBP alone or SLG% alone.