I agree. Average defense to me is getting to routine fly balls. I don't recall many triples hit into left field, that is very hard to do.
Just me (and the rest of the scoutheads, I'd guess) but I honestly don't care where his WAR, oWAR, or any of his other advanced stats wind up. Again, that's not to knock advanced metrics. I'm mainly interested in the other things you've mentioned - 30+ bombs and 100+ RBIs hitting behind Freddie in the lineup and not being a complete butcher on defense. Keep those triples down (LOL) and get to most of what an average LF should get to, and I'll take it.
Serious question, who's the less valuable player - Kemp with his offensive numbers in LF or Asdrubal Cabrera and his not particularly good defense at SS? Pretty easy choice for me.