Clutter is a real thing, but it's something that's present all the time when it really should not be and is so in an obstructive way, such as ads, locked out premium features, reminders of premium features they want you to buy, wasted empty space, etc. In contrast something like a settings menu definitionally cannot be cluttered (at worst it can be disorganized or poorly labeled) because it's something that's rarely touched and which needs to be exhaustive in its contents.

So apps tend to be actually extremely cluttered in bad ways (because monetization is real clutter), while also being infuriatingly barebones. They're the actual worst thing and should simply stop being a thing.