So much to say about WAR, so little time. Who am I kidding? I have all night.
1. Just because a stat is flawed, that doesn't mean that it's no good or worthless. The fact of the matter is that WAR works. It correlates very well with actual team wins. Like it or not, IT WORKS. All stats are flawed one way or another. That doesn't mean that they're all worthless.
2. Every offensive statistic is subjective as well. Ks, hits, OPS, you name it, it's subjective. Offensive stats may not be as subjective as defensive stats are, but they are subjective nonetheless. The stat geeks go through painstaking measures to eliminate as much bias and subjectivity as possible, and they do a pretty good job of it. A much better job than an official (biased) scorekeeper or even an umpire calling balls and strikes do.
3. I have often heard people state that WAR overvalues defense too much. IMO, I think WAR has it right, and most people undervalue defense too much.
4. One of the best things about WAR is that it gives us the ability to compare players who play different positions, including comparing pitchers with position players.