That is how we did create such topologies. But if we had not, could they have been discovered through neural architecture search [1]? NAS has been used to find architectures that outperform those that were hand designed. And in RL , Google used a method inspired by NAS [2] to learn methods built by hand (i.e. TD learning, DQN). I know it's not the same but if you use a bit of speculative imagination you can translate what has been done to signal processing applications.