Honestly this all sounds very old fart “they don’t build them like they used to” and “back in my day”. That isn’t to say I disagree with the sentiment entirely. But:
A hidden button doesn’t clutter up what the user interacts with so long as the user knows how to find the button. I like clever interfaces after I figure them out. I don’t like them before because they make me feel stupid. But as soon as they make me feel smart after I figure them out, I suddenly enjoy them so long as they meet the second goal: make me productive. Take Snapchat for example. It has a really clever UX where you tap on your face and it will bring up filters. I honestly don’t know if there is a dedicated button for this somewhere. I certainly felt dumb right up to the point where someone showed this feature to me and and then it felt very neat.
So maybe when the pendulum swings from clutter-free to discoverable again we could find some compromise between 1000 buttons on the screen that all do something and no visible buttons and figure out clever AND discoverable interfaces.
And before yet another startup with their idea for a UI walk through GUI pops up, no those things aren’t the answer. They suck and I would prefer they didn’t exist. If your UI needs it, you designed a bad UI.