Indeed. One reason why ML is quite powerless when looking at the stockmarket (from the point of view of past stock values) is that, even if you assume there is

Indeed. One reason why ML is quite powerless when looking at the stockmarket (from the point of view of past stock values) is that, even if you assume there is a latent model to be learned, it would seem reasonable that this model evolves as fast as the economic landscape and that is to say, quite fast. To such an extent that the valid data points available (the past few years of price variations) would not suffice to train even a very low-dimensional latent model.