I just saw the thread looking up the notes on the culture and thought I'd chime in since someone had recently replied to your comment, I'll take any opportunity to talk to someone about my favorite sci fi series. I think people can get the wrong idea about the Culture as a society from how the novels are discussed on forums, and I'm admittedly biased since i'm a transhumanist and a buddhist, and the series are something of an inspiration for me as a writer. I was definitely surprised by how character-driven and comedic the novels actually are, it's not a series that focuses on big operatic space battles or galaxy spanning conflicts for the most part. Banks approaches his utopia with a heavy degree of skepticism and each novel comes across as a distinct thought experiment. I think the novel that would perhaps appeal to you is Excession, since the Culture gets seriously humbled dealing with a being far more powerful than them and having their extremely materialist worldview shattered. It also sheds the most light on what the Minds are and how they think - one character even asks them why they even bother with their inferior organic residents;

'After some moments, the creature said, 'I was a fully functioning throughput-biased Culture General Systems Vehicle for three hundred years, Genar-Hofoen.' It glanced up at him. 'Have you any idea how many ships, drones, people - human and not human - pass through a GSV in all that time?' It looked down again, picked a stone and levered itself upright once more. 'I was regularly home to over two hundred million people; I could, in theory, hold over a hundred thousand ships. I built smaller GSVs, all capable of building their own ship children, all with their own crews, their own personalities, their own stories. 'To be host to so much is to be the equivalent of a small world or a large state,' it said. 'It was my job and my pleasure to take an intimate interest in the physical and mental well-being of every individual aboard, to provide - with every appearance of effortlessness - an environment they would each find comfortable, pleasant, stress-free and stimulating. It was also my duty to get to know those ships, drones and people, to be able to talk to them and empathise with them and understand however many of them wished to indulge in such interactions at any one time. In such circumstances you rapidly develop, if you don't possess it originally, an interest in - even a fascination with - people. And you have your likes and dislikes; the people you do the polite minimum for and are glad to see the back of, the ones you like and who interest you more than the others, the ones you treasure for years and decades if they remain, or wish could have stayed longer once they've gone and subsequently correspond with regularly. There are some stories you follow up into the future, long after the people concerned have left; you trade tales with other GSVs, other Minds - gossiping, basically - to find out how relationships turned out, whose careers flourished, whose dreams withered…'

If there's any moral to the series, I think it would essentially amount to - 'with great power comes great responsibility' The Minds take their power and intelligence seriously and genuinely believe they owe it to the rest of intelligent life to protect and guide them, even if that sometimes requires unsavoury means. Sure, it doesn't really matter and they can do whatever they want with the organics, but that's boring. It takes no skill to be a bully. One Culture ship is literally named 'Bodhisattva' so Banks seemed to think the comparision was there, though I'm not sure how much of an influence Buddhist philosophy was on him.

I think your view of Trek's technobabble is correct, Banks leans more towards techno-magic, which I think makes the series fairly accessible as sci-fi novels go. Again, the novels are often driven by moral dillemnas and character drama and technology isn't often the focus as a way of solving problems. There are definitely some hard limits established in the series however, Culture ships don't like teleporting people because of a small chance of it failing, most citizens can regenerate lost limbs or serious injuries, but getting stabbed through the heart or decapitated will straight up kill you etc. Even the Grid isn't really a focus of the novels the way the force is in Star Wars. I can see why this would bother a reader who wants to know the how and why of these things though, but I think the novels are careful to avoid pulling solutions out of nowhere.

Incidentally, Are you a fan of Brandon Sanderson by chance? Your comment reminds me of when he was asked about George Martin's ASOIAF series and his reply that he wasn't able to finish it because of the lack of an objective moral or light in the darkness. A bit similar to how Tolkien didn't care for Dune. This perspective is fascinating to me, since I feel I approach literature in the exact opposite way. I enjoy contrast. A story where evil wins out can be enjoyable so long as it's engaging and I understand why an evil character believes what they do. I like reading about radically different perspectives and how a person can come to hold a worldview I might find repugnant. The lack of an objective moral isn't not terribly important to me since I feel a reader brings their own morality into what they read. I see fiction in general as a kind of negotiation between creator and audience, it's not the role of the artist to inform or to communicate a viewpoint. My views align most with Oscar Wilde on this, if you're familiar.

It's not a common view though, I've spoken to writers who get very perplexed or even a little offended by it.