I attended a conference talk of a FB AI-engineer talking about her paper with backprop equations so obviously wrong my eyes hurt, and incorrect definitions of objects. It did not stop her from participating (btw. this is always unclear -- who did what) in state-of-the art research in object detection.

PhD is overrated in the deep learning context. It is more about forging the intellectual resilience and ability to pursue ideas for months/years than learning useful things/tricks/theorems.