Well those people are wrong. There were Islands everywhere to explore for stuff like larger wallet/more arrows/bombs/etc, they had sharks that would attack, the treasure hunting, outposts, and on and on. If you couldn't find something to explore, you were doing it wrong, and even then, it was so fun just sailing the open sea, kind of like you said with the trains, it was very relaxing, and the music was the series best yet.
EDIT: I'm kind of defensive when it comes to Windwaker, it's my favorite Zelda game by far,
EDIT: I'm kind of defensive when it comes to Windwaker, it's my favorite Zelda game by far,