It's a high enough percentage that I suspect anyone who really enjoys SN is doing what you (and I) do and trying to control their feeds with mutes, subscriptions, etc.

That said, it's all a feeling and anecdata (for me, at least), and I'm not sure if the number is as high as my gut tells me.

(Also, of course, there's a chunk of SN that is not sat-farming, and might not even be garbage, but just are not for me, and both kinds of posts trigger the same "noise, not signal" reaction in me.)