That's a very good observation. However, deep learning didn't just get the share of the first mover. Before DL was popular, Support Vector Machines used to be w

That's a very good observation. However, deep learning didn't just get the share of the first mover. Before DL was popular, Support Vector Machines used to be where all the ML fun research was happening. And just out of nowhere, Random Forests and XGBoost came and took the crown if only for a fleeting moment. Gaussian Processes always showed promise, but I'm not sure they delivered. Deep Learning just delivered. I guess it's because of the composability. But you are absolutely right that there's no proof and now way of knowing right now if DL is the best there possibly can be.