It’s based on your viewing history.

You can run a little experiment to verify this if you want. Take some subject you usually watch and take some channel your have interest in (and you will keep watching similar videos). Set that channel as “don’t recommend channel”. After a while (never calculated how long), you’ll get recommendations of that channel again.

I also don’t get Mr Beast recommendation as I don’t watch similar content, but there are channels I need to keep blocking since I like the subject but not those channels in particular.

I was mostly just saying that the “don’t recommend channel” approach is not a solution for everyone.