This is not true. You can in fact block specific channels. From YouTube support[1]: > On certain pages, such as your Home and Watch Next pages, find a video from a channel that you don’t want recommended to you.

> Click More next to the video title.

> Select Don't recommend channel .

[1]: https://support.google.com/youtube/answer/6342839?hl=en

And the community posts and polls from random communities you have no interest in and don’t give you the same “don’t show me content from this channel”