Really high quality writing for its time.
The original Star Trek was Roddenberry's vision of utopia. The benevolent dictator always makes the right decisions. He's surrounded by his loyal band of perfect lieutenants, who apparently have zero desire to advance, and have no flaws at all. Any and all of them are willing to sacrifice themselves for the others. None do anything bad (unless it's a plot device with an explanation that absolves them).
Don't get me wrong, I've enjoyed watching ST very much. Just keep in mind that that it's a fiction.
Utopias used to be the most common scifi futures. This is what the so called Cyberpunks (Sterling, Gibson, Cadigan, ...) rebelled against.
It used to be all about what wonders technology will bring us. By the time of the 70s it became clear that technology doesn't necessarily make everything better, but can be a burden in itself, or even widen the gap between the haves and haves not. And that is what they wrote about. It turned out to be the most popular scifi with audiences deeming it more believable.
Some say it was the last sci-fi utopia in modern pop culture.
That is an oversimplification and simply not true at face value.
'The original Star Trek', even less so! Very morally questionable at times. In TNG, you are watching the flagship of Starfleet, it's the most coveted starship. The crew are the best they have to offer. It's obvious that they would be the most professional. Even then, they make mistakes, often serious. Sacrificing themselves - if needed - is part of their job too.
Riker does spend a long time on the Enterprise, even after being offered command a few times. He does eventually move on.
Maybe they are a little too perfect, but I'd argue that's for the best. The moments where there's friction within the crew are much more memorable because of it.
Thats in contrast with some newer Trek which have more conflicts than Stargate Universe characters and would be considered way too unprofessional even if they were Lower Decks characters.
I don't think TNG is as simple as you make it out to be. All of the characters have serious flaws. Picard does make mistakes (including some very serious, consequential ones). Characters do get angry, jealous, etc. and do bad things. Sometimes their friends help them overcome it, other times they figure it out on their own, etc. It's episodic so it usually goes back to the status quo, and that can feel kind of trite through today's lens. But it's exactly that ability to solve problems (technical, emotional, organizational, etc.) as a team that's so compelling for many of us.
It was actually quite pleasing to see the subplot of them them repeatedly failing until they got out of their predicament by other means.
It's a rarity to see something like that in fiction.
Don’t get me started on their engineering that causes a matter-antimatter runaway reaction if their fuel tanks ever lose power. And routing discharge-prone HV power lines behind the bridge consoles, or placing the bridge on the outer hull.
I love it, and I know this is all in the service of the story, but I will not give Starfleet a pass for that kind of irresponsible engineering.
Most of the characters in Star Trek are members of the military. So of course, there's a chain of command and orders have to be followed.
The Federation of Planets wasn't a dictatorship.
And they aren't even really members of the military. Starfleet is canonically not a military force, its purpose is exploration, science and diplomacy. It just happens to have a military chain of command, and ships with military designations bristling with planet-cracking weapons. That get into battles and fight wars a lot.
Ursula K. LeGuin
Whereas Voyager, which was written after Roddenberrys passing, leaned heavily into inter-crew disputes.
The best dialog ever:
Lawyer: Mr Spock, I understand you know something about computers?
Spock: I know all about them.
Always makes me laugh.
DS9 did good in adding a bunch of non star fleet characters who had maybe more realistic motivations. Voyager tried but immediately just turned them all into a big happy family just like TNG.
That's why Orville is my favorite of the newer ST series. It has the high moral standards of the original series, but with characters who are far from perfect, who make mistakes, and who are sometimes even a little weird.
In other words it only works because it ignores basic human nature. Which is one reason why Star Trek's utopia isn't really tractable. The others being the technology that completely ignores the laws of physics. Free energy, warp drives and magic boxes that grant wishes.
If people want a science fiction "utopia" I'd say look at Babylon 5. It certainly has its flaws but its Utopia isn't real (because they never are,) it's an ideal that people are always struggling towards.
I find it somewhat plausible that this could actually lead to something like the show depicts. There is precedent for sweeping moral changes in human history. For example, large parts of the world now find practices like torture, slavery, and collective punishment to be repugnant. Those practices still happen to some extent, but they're not viewed as being just normal like they generally were seen back in the day.
Another example is how Europe and Japan after WW2 genuinely became more pacifistic. Not just as a pretense to fool outsiders, but as a genuine change in how the inhabitants see things.
Picard viewed the power of leadership as, foremost, a responsibility. Every action was careful, deliberate, and well advised. Some later Trek shows (e.g. Voyager) turned captains into geniuses who knew more about everything than all of their underlings. Picard was not an expert in most things and needed his staff to advise him. Once he knew the options and consequences, he shouldered the responsibility of the outcomes, but as a leader of a crew, not a genius with compatible lackeys and minions around him. It was a realistic take on leadership that simply doesn't appear often in television or movies.
Stewart, of course, was not Picard. It's too easy to conflate actors with their roles. However, actors do often help shape their characters, and Stewart's ability to give a thoughtful, diplomatic, and prudent character such incredible power and presence is likely what made Picard possible. The showrunners didn't need to strap a phaser to his thigh and drop him into every away mission to make him compelling because of what Stewart was able to accomplish as an actor sitting behind a desk.
Not everything. Picard was command track his whole career, I think the same was true for Sisko. But Janeway started as a science officer before switching to command, and Archer was a test pilot. Their experience in those fields would sometimes be useful. It's similar to how Picard's interest in archeology was sometimes useful.
Roddenberry was after someone younger. There’s even a casting show reel of Stewart wearing a toupee and speaking with a very bad French accent.
Really high quality writing.