The over said "No plan/adventure/story/plot survives contact with the feral players, so you should just improv random stuff out of thin air to make the greatest game play ever".
And the follow up "the game is whatever the players randomly do on a whim and the GM should just follow along and create and recreate the game on each players random whim"
That said, both of them are bad only because they are extremes, not because they contain no truth at all. It's true that no plan survives contact with the opposition (be that GM plans opposed by players or player plans opposed by GMs!), so being
prepared for improvisation is essential--but "be prepared to do X" is a far cry from "never do anything
but X." Likewise, one absolutely must not, under any circumstances, take the problems of the second thing to mean "caring about what your players want to do is bad, so never ever adapt to your players' interests,
especially if those interests don't make sense to you." Because doing that is a one-way ticket to pissing on genuine player enthusiasm and feeling good about doing so.
As C.S. Lewis said, “Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. [...]those who torment us for our own good will torment us without end for they do so with the approval of their own conscience.”
I draw the contrast here because my thing above--"you're the DM, you figure it out"--
is inherently a problem. That message, very intentionally and explicitly, rejects the very
idea of seeking advice, developing skill, and aiding others. It cannot be softened without abandoning that core message, at which point it becomes something like, "Well, as DM, you have the power to make that decision and whatever you say will be 'correct' for your table,
but if you would like some help, <advice.>"