One of the characteristics of mass-market advertising / propaganda, is that it's Big Lie / Big Message dependent. That means that at any one time a relatively small list of channels is responsible for the majority of chum. Thank power laws / Zipf functions.

Of course, there's enough channel-churn that these do turn over relatively quickly, but that tends to be on the scale of weeks to months, not hours to days.

Once you've knocked off the major chum sites, legitimate channels start rising through the noise floor. The small-scale chum sites tend not to turn up in high rotation.

Channel-block should be an inherent function. Web search also desperately needs this at the domain level.

(I just ran into this looking up a hiking trail. First-listed site, which dominated my search results, splashes up a registration wall on following any links. Peakbagger, buried in the search results, does far better. I also had to block Pinterest, of course....)

I have very narrow interests for video topics and it works for me at least. Of course it's not perfect since new channels will pop up, or youtube will suggest new topics (e.g. lately the johnny depp trial), but even then, you can block 90% of it quite easily which is already a big improvement.