That's not entirely true. The TOS people were incredibly improved - so much so, that the concept of honest racism was so alien to them, they only knew it from history books. McCoy often made mocking remarks about Spock's heritage. But the thought that people actually meant that way of thought (from the two-colored aliens to space-Lincoln) was so alien to them, it had to be explained. Similarly the concept of regular crime, poverty, class divide, common disease and all that was merely theoretical for them.
They were still very, very human all the time though. They had anger, emotions, cracked jokes, and displayed very human behaviour all around.
TNGs humans seemed weirdly cold. They didn't grieve, fight, or mocked each other. We were also told that was "evolutionary", which was weird, whereas Kirk & co.'s superiority was clearly learned behaviour.
All around I'm happy Trek went back more to the TOS approach of "real" humans. But I think they overcorrected, and missed that even TOS' humans were incredibly advanced - even by today's standards, let alone the 60s.