Cross Validated seems to be interested in only a subset of machine learning science, particularly the established machine learning methods that apply to data analysis in the narrowest sense. You will not find there many (if any) topics on machine learning as it relates to cybernetics (for example, systems control and robot control) or computational neuroscience. You will find only meager treatment of the subject of neural networks, which, apparently, is not a contemporaneously powerful approach in statistics, and yet is obviously important for other reasons.
For an example of the comprehensiveness with which Cross Validated treats machine learning, see this response to the question Backpropagation algorithm, which is possibly one of the most significant algorithms in the history of machine learning.