Well, of course, Neil had a very deliberate approach to his composing. He wanted to write very commercial songs that sold millions. And, he achieved that.
He wrote for the times. composing catchy 2min30sec songs that would appeal to teenagers.
He wouldn't have seen his songs as great works of art ( after all, he was the precocious kid who could play Chopin and Bach, beautifully ) but within the musical confines of the day he did push the envelope - harmonically - quite a lot.