a couple months ago they were brutal with making every video "not advertiser friendly" and you had to appeal. for a site like mine, which is not evergreen at all, but mostly current, it killed our income as we could get tens of thousands of views that got paid nothing. and none of our videos are "not advertiser friendly." its slowly returning to normal and when our videos are flagged, they usually get through the review quickly. as far as i know, nobody is getting demonitized for months anymore. at least not legit channels.
as for banning channels, a lot of them are for people trying to game the system and cheat with views, clicks, etc. thats why i say i dont tinker at all with anything. you never know what will set them off.
the music does suck. we film a lot in the gym and some song can be playing in the background and the next thing you know Jay Z is making money from our video because you can barely hear his song in the background. But that doesnt happen too much. when it does, i just mute the video and put royalty free music over it (as long as it is just training footage).
the tv shows posted you see might have ads, but they could be put there from a studio that claims rights. they dont have to take the video down, they have the option of just taking the money. people that dont get flagged usually mess with it to avoid detection like speed it up, slow it down, reverse it, etc