I keep up decently with things - not as a lifestyle, but pretty much my only YouTube push notifications are leftist progressive independent news - and if I’ve heard of the John Birch Society before, I’ve since forgotten about it.

This is not to say my experience is typical, or that your assertion is wrong. Just providing an additional data point.

Edit: I imagine “progressive” is a better descriptor than “leftist” for the media I consume, as I can’t think of any actual socialist voices among what I watch.