Like / Dislike is the rating system evolved, there was an article about how they had come to the decision through research that a 1 - 5 rating system doesn't work; people more often than not either like it or they dislike it, so 1 and 5 were the common votes.
If you want to be pedantic then sure, they removed a core part of Youtube when they removed the rating system, but in reality the system evolved. 1 - 5 was (at it's core) a way to rate videos: like / dislike is (at it's core) a way to rate videos, the interface and finer points are different but it's still the same thing overall.
Google doesn't care what info you put in when you sign up for a "normal" account, they just use it to correlate interests for ads and recommendations on the site. But to sign up for Google+ you have to use your real name or risk being banned.
If you want to be pedantic then sure, they removed a core part of Youtube when they removed the rating system, but in reality the system evolved. 1 - 5 was (at it's core) a way to rate videos: like / dislike is (at it's core) a way to rate videos, the interface and finer points are different but it's still the same thing overall.