But it's not just about open chords. If you strip down a Bm7b5 to a Bm and play the Bm on the second fret it still has half of the character of the Bm7b5 chord.
Only recently did I start gaining the patience to learn every suggested chord and it makes a tremendous difference.
That said, I prefer piano for accompanying because the piano's tone is somehow more forgiving with basic chords than guitar is.