An ML algorithm that can be reused for both recognition, generation, and novel generalization tasks is already a step above most of the entire field.
Classification of high-dimensional data is a huge portion of machine learning.
>They reduce the search space by limiting themselves to combinations of typical pen movements.
"They reduce the search space by limiting themselves to gradients of nearby pixels. Very smart, but I don't see how convolutional neural networks can be applied to machine learning in general."
All of machine learning involves some prior knowledge -- the question is always how much and at what level of abstraction.