As an programmer, I want to think out loud about possible technical solutions.
I would have kept the understandable / hand-made algorithm as the core of search results. If you want to do fancy machine learning, do it on the periphery and we can include the machine output in our algorithm and weight its importance by hand. This would allow us to back out of the decision, because we could lower the weight of the machine learning output as needed.
It sounds like Google jumped strait to including the machine learning in the core algorithm though, and now with a decade of complexity in the core algorithm they are no longer able to go back without huge effort.
In general, it's important to consider "is this a decision we can easily back out of?".