It's not simple to do next token prediction. That IS what is going on. You want something 'deep'. Deep things are often very not complicated.

The deep realization is that if you can predict the next token well enough, you can do things like this:

<paste the first 10 chapters of a mystery novel>. And it turned out the killer was

And if it's really good at predicting the next token, it has to understand the novel and the clues, which means understanding the context and the language and human norms and innuendo and story telling, and tropes, and red herrings, and predict who the killer was.

I think you want it to be something more complicated. It's literally not. It just turns out predicting the next token is equivalent to a universal compression algorithm, which is a form of general intelligence. And we have almost unlimited 'labeled' data to train autocomplete.