But the particular quote is referring to learning rates in autonomous robotics, especially visual classification in complex real-world scenes.
I have worked and published in ML since the early 1990s, was a program chair for the learning track at NIPS one year, participated in the same DARPA learning-to-drive program that Yann LeCun did, and don't consider the math behind "state-of-the-art papers" to be simple.
Just taking deep learning: there are a lot of tricks and recipes (e.g., rectified-linear activations, number of layers, staged training) that are not mathematically understood. It's exciting, but mathematically still a jungle. Just because a neophyte can code and optimize a network does not mean that the math that explains why it actually works is simple. As engineers, we need to understand why it works before using it in a safety-critical situation.
Someone who has digested enough of the AI literature to think about the methods in aggregate is very likely to be in a position to see any particular method as a "simple" implementation of some more general set of principles.