But still you have to explain why your code is the way it is on top of that. You can always deduct the what from mentally processing the code, but you can't deduct the why, you only guess.

Definitely agree there are still cases where "what" is useful. Especially in some code that I come across that I just can't grok (e.g. badly named things), I start writing what it does just as a rubber duck method, and I don't have capacity to refactor the whole thing right then, at least I will leave behind a "what" comment because if I had trouble grokking what it does then someone else likely will too.