If Kirk is so bad, why is it everyone, EVERYONE, knows who he is, and knows his solos inside and out? Because the truth is, you liked it too, and it probably was part of your introduction to guitar playing like millions of others. Ever wonder why people like it so much? Because it's not too complicated that you have to be a seasoned pro to play, and it's fun and easy to get into, and I think many just outgrew Metallica and Kirk's playing. He never claimed to be the best or the fastest, or the most technical, in fact I've never heard him claim to be anything other than the lead guitarist for Metallica.
Just because you have outgrown it and moved on, does not make it crap, and that's really the issue here. You should never forget where you came from and appreciate these guys for getting you into it, but instead all these self appointed "pro" musicians that have done nothing of mention, say he's not doing it right, and he's terrible, y'all need a reality check. He's the famous one in the band Metallica, and they sold over 10 million copies of their last album in an age of piracy and then toured sold-out shows for 5 years straight, got inducted into the rock and roll hall of fame, made a 3D movie, organized and headlined the Big 4, did a 30th anniversary gig, made a world record when playing Antarctica, played the Grammy's, made the move to Fractals/Digital, and this is just the bigger stuff.
How is it he's done all this and more while being the worst guitar player in the world? James is a god, we all know this, but without Kirk it's not Metallica.