I think you could have done this in the 1980s and 1990s and found a lot of fits: MTV, reality shows, daytime TV, junk food everywhere, pop music becoming increasingly trite and simple, newspapers and commentary declining toward grade school level vocabulary.
In the 50s you would have had suburban conformity and doctors recommending cigarettes. In the 60s you had people trying to become enlightened by taking drugs and listening to con men claiming to be Eastern gurus. In the 70s you had dumb new age cults and a lot of very bad movies and ugly fashion.
Mass media and any culture dominated by mass media tends to race to the bottom. There are many forces that drive it. Dumb culture is loud and viral. Lies and bullshit cost zero to produce and are expensive to debunk. Quality takes time and cost to make and drowns in quantity.
Attempts to frantically fight these forces normally turn into their own dystopias, usually taking the form of authoritarian nightmares or moralistic crusades. These often end up looking deeply stupid in retrospect too.
Yet we are still here. So somehow quality finds a way.
As you look back in time things look less dumb because of survivorship bias. The dumb shit is forgotten.
Our age will be remembered as when we taught the sand to think, made rockets that land vertically, returned to the Moon, and developed quantum computers.
Nobody will remember that we used AI to make TUNG TUNG TUNG TUNG TUNG SAHUR, that the guy with the rocket company acted like a thirteen year old 4chan edgelord, or that our president during the return to the moon couldn’t speak complete sentences.