You don't hear a lot about them nowadays because the hype now is ML, even though things like search or decision tree are probably more widely adopted than ML.

You don't hear a lot about them nowadays because the hype now is ML, even though things like search or decision tree are probably more widely adopted than ML. I believe things come and go in cycles, so we might see the rise of non-ML solutions if the current circumstances change. Just like the last time: https://en.wikipedia.org/wiki/AI_winter https://en.wikipedia.org/wiki/AI_winter.