Zoro isn't a very complicated character and he doesn't need to be tbh. I agree with some of your points but disagree with a lot. He's kind of like the perfect character in a manga- strong, badass, loyal and hard working with almost 0 flaws. I personally am not a big fan of such 'perfect' characters, especially when they provide little comedic relief (though I used to be when Zoro was my favorite character long ago). But most people like such characters so there's no harm in it, at least from a money making perspective.
He's still a top 3 or top 4 straw hat for me and will probably always be. In short, yeah, Oda can do a better job but he's a good character for the most part, at least at what he's meant to be. I would like him a lot better if he had any major flaw as a character like some others which could be resolved later or at any point in the story. He never had one iirc.