Doctor Who for example is extremely optimistic and one of the more popular sci-fi properties active today.
Dr Who is produced under the BBC system where the response of the viewing market is not the determinate factor in it's continuation. Yes it has a measure of popularity but it also has powerful insider friends who advocate on its behalf to the program deciders.
The Stargate shows had their heyday 10 to 15 years ago and were very optimistic.
Just as I said, better part of a decade and a half ago, NOT the modern SF market.
Firefly, one of the most talked about sci-fi shows of the past 15 years is largely optimistic, it just isn't a utopia.
Apparently you haven't actually watched the show. It's about losers who REMAIN losers and down at the bottom. That's how Joss DESIGNED the show, and he's said as much.
Finally, one of last year's most popular sci-fi movies Guardians of the Galaxy has no cynicism or despair in it at all. In fact, Paramount allegedly wants the next Trek movie to be like GotG.
Superheroes are not sci-fi. And we've had two "superheroish" Trek films already, and they were lightweight and unimpressive.
I think you're looking too hard to see thing which aren't there. Sure, I love Star Trek, it's a great and entertaining series of TV shows and movies. But it's not the kind of deep intellectualism everyone makes it out to be. And some of the more popular episodes and movies of the franchise are the ones that are straight action fare such as Arena, The Doomsday Machine, Yesterday's Enterprise, The Best of Both Worlds, TWOK, TUC, First Contact, or lighthearted comedies like The Trouble with Tribbles, Q-Pid, or TVH.TMP - Is the physical all that exists? Are we nothing more than the components that made us?
WOK - What does a man who has spent his life cheating the odds do when the odds can no longer be cheated? What does a man do when he is confronted with the life he could have had?
SFS - What is the value of one man's soul? How far will a person's friends go to save him?
TVH - What price might we pay tomorrow for our foolishness yesterday?
TFF - What is the nature of God and faith?
TUC - What happens when two groups who have hated each other for years have to work together to solve a crisis? What will one group do to another when they have them at their mercy? How will individuals within those groups face their own inner prejudices and can they overcome them?
GEN - How does a man come to grips with what he sees as the end of his useful life? What can happen when a man holds too dearly on to the past and refuses to look forward? (again) How does a man confront the "roads un-traveled"?
FC - The terrible price of obsession. How do people respond when they find that their heroes are just normal men such as themselves? How does a man who has lost so much in his life that he has become bitter and cynical find new hope?
INS - How do people who have become too busy in their lives learn to slow the pace and actually live those lives? What rights do majorities and minorities have when their needs conflict? What is the "greater good"?
NEM - What is the controlling factor in a person's life? Nature or nurture?
The various serieses had no shortage of topics to comment on either, ranging from terrorism (The High Ground, any Maquis episode), to the ethics of war (In the Pale Moonlight), bio-ethics and human experimentation (Unnatural Selection, Dr Bashir I Presume, the "Jack Pack" episodes), the unintended consequences of changing environments (Home Soil), ethical considerations of intervening in the lives of others (Pen Pals), torture (Chain of Command), recovery from horrific violations of person (Family), and how "saints" react when brought face to face with a decidedly "unsaintly" universe (Homefront, Paradise Lost, Siege of AR-558).
That's just off the top of my head.
Arena is not a straight action show. Kirk comes to understand the trait of mercy, and examining situations from other perspectives, rather than blindly waving the Federation flag and "gung ho"-ing his supposed enemy.
Doomsday machine examines how guilt can affect a person, especially a leader.
And I already listed the philosophical/moral/ethical issues examined by WOK, TVH, TUC, and FC.
Those issues are real and they are there and boards like this have spent pages and pages and pages of posts examining and debating them.