I think much of the song arrangement is likely from Lars.
There is a video somewhere of Hammett describing how he shared a riff for one of their songs and Lars said "play that but 3 times them end on that" or something to that effect.
Live performances may not be super tight but it's OK because Hetfield is a better drummer (at least he keeps the rhythm)
For sure, the band is Lars and James. People like to hate on Lars and Hammett out of jealousy I guess, they’re both really successful in a genre that celebrates technical prowess, while not being technical players.
Also most of them are software engineers and I don’t think they would like to know what I think of their code and documentation.