No.1 Apparently not present on uBlock Origin, which makes it not a problem for me (though it's shite that they are doing it anyway). I don't use YouTube that often anyways.
No.2 You are not loosing a lot - it's most likely some crappy video about a guy slipping on a banana peel or some shit like this - 99.9% you are not missing on much :D
See as much as I dislike the company, I can see how it would make sense from a business and logic point of view. They are paying for the servers and, to some extent and form, for the content, and by using any ad blocking content you sabotage their earnings from this platform. I'm surprised they are not blocking browsers with said plugins, but that would cause a major uproar. But then again, not much competition around...