I've so far only read Consider Phlebas, and while it's an interesting dystopia where humans have no purpose, and machines could do everything (if allowed), it's not an actual interesting story.

It's like he had the idea for the dystopia, with the main character fighting against the machines. And then tried to write a story around it. The central idea is interesting I guess, but the story built around it is not.

It doesn't help that the fight is futile, the machines as described are so powerful humanity doesn't stand a chance, so what kind of story can you make?

Maybe the later books are better.