Classic AI can definitely be deterministic and knowledge-based. It just sounded from that phrasing like you went down the "explainable outputs" route that is sometimes a part of such approaches (see expert systems, for example) and that is commonly missing these days (which may lead to people using outputs of complicated decision-making systems asking questions like "why would we want to do that?").
We don't currently use any AI - we're yet to exhaust deterministic knowledge-based algorithms, but it might be something we look at in the future.