I do feel somewhat bad rating this Fitzgerald book with such few stars. Here's the thing - I admire his writing style, and find it interesting. But that doesn't make me like his characters or plot any better. I completely think this is a great book to teach with (and agree that yes, it is a classic) because of that - you can often have wonderful discussions when you dislike characters, or even an author. But as for something I'd pick up and read again and again? No. I've spent enough time with these particular characters, and even on rereading years later felt pretty much the same as when I first read it on assignment. If I was going to read more Fitzgerald I'd rather reread some of his short stories.
You could actually make a very good argument that we're not meant to like any of these characters, and only empathize with the narrator. In fact I'm pretty sure that's what I did in one of my school essays.
(I feel similarly about Hemingway. Brilliant writing style, completely agree his works are classics. I just don't want to spend more time with the people he creates.)