Big time agree with fiveofswords.
Also I think some of the really classical lines (some close to 100 years old!) are... well at least to my amateur eye... are objectively better than what's played today. It's just GMs avoid them because they've been analyzed to death and they'd rather try something new and dynamic on their opponents.
I'm keeping an open mind. I have only tried KIA 1.Nf3 a couple of times. I typically open with 1.d4 (used to open with e4). Maybe I should learn KID. I need more input from people, articles, etc. I'm still at the point where I can be molded...I don't know what my repertoire should look like (not that I can't change it later).
As a KID player, don't learn the KID. Not yet. There are less demanding options for fighting 1.d4...use that extra time you'd need for learning KID theory and use it on endgames.