the.com/mainstream
The river everyone swims in, which is why nobody notices the water.
means The ideas, tastes, and trends accepted and consumed by the majority at any given time.
from A literal term for a river's main current, surfacing in the 1600s, then borrowed by the 1800s to mean the dominant direction of thought, culture, or society.
Mainstream jazzA real genre, coined to label the unpretentious middle.
Moving targetYesterday's rebellion becomes today's mainstream, reliably.
Media usageThe phrase mainstream media barely predates the internet.