As far as I understand it, determinism is about being able to predict the next state if you have all knowledge about a system. That we can't have all knowledge

As far as I understand it, determinism is about being able to predict the next state if you have all knowledge about a system. That we can't have all knowledge about most systems in the real world doesn't mean they're not deterministic. And who knows what kind of magical science we'll find in the future that turns everything we know about measurement upside down?