A simple statistical system based on a lot of data can arguably still be called a simple statistical system (because the system as such is not complex).
Last time I checked a GPT is not something simple at all... I'm not the weakest person understanding maths (coded a kinda advanced 3D engine from scratch myself a long time ago) and still it looks to me something really complex. And we keep adding features on top of that I'm hardly able to follow...
