Most of TNG painted a picture of a perfect utopian Starfleet and how humans had grown up, like you say . (Obviously, humanity is never perfect but the messaging is fairly clear: They try.)

I can chime in more about VOY and ENT though....

VOY is my favorite and also when you start to see a little more of humanity in Starfleet. We learned a few things like: The Prime Directive/Temporal Prime Directives were always just suggestions, murder could actually be justified, you will never get promoted past ensign if you play the clarinet and chemical addiction is still a key driver in human decisions and behavior.

ENT is just the human transition out of a military focused race to a race focused on exploration. (I am not sure why Archer always seems to have serious case of constipation, but it is what it is.)