I noticed the first few seasons of TNG and TOS had a heavier dose of utopia descriptions.
I don't think these ideas are worse or bad ideas, but a question of how realistic or rational the ideas are.
According to TOS, future humans don't get angry at insults anymore at all. They don't fear words.
The Neutral Zone (TNG), claims 24th century humans don't fear death, they're much more evolved than that.
Then you have the no need or want in the 24th century--humans had 'grown out their infancy'.
That sounds like humans are living in a virtual Eden getting all their needs provided for free.
And Starfleet is not the military- it is an exploration vessel that carries families and children, but will take care of military duties if necessary--with the children on board.
Is it realistic or utopian, or both?
I don't think of it as a utopia. A utopia by its very definition is stagnant and boring. I think Roddenberry's vision was of humanity working to constantly improving itself - striving toward perfection, even if perfection itself is unreachable.
And yes, the Federation does seem like an Eden by modern standards, but think of when it takes place. A lot of people seem to forget that Star Trek's setting is not 20 years in the future, not 50 years in the future, it's THREE CENTURIES in the future. A lot changes in 300 (or 400) years.
Most of our lives are like an Eden compared to life three hundred years ago. Our world is not perfect, but we have more freedoms and opportunities than ever, and we are (slowly) working toward equality. In many respects we in real life are living out Roddenberry's vision.