> NN's are ~general non-linear functions which polynomials are very poor at representing This is not true. Deep ReLU/leaky ReLU NN are piecewise polynomial fun

> NN's are ~general non-linear functions which polynomials are very poor at representing This is not true. Deep ReLU/leaky ReLU NN are piecewise polynomial functions generated in a contrived way (a chain of compositions). Even if we assume that piecewise polynomial functions aren't polynomial functions, they are still in the same class of linear functions.