Here is where the idea goes off the rails for me:
"Since the majority of its biological population can have virtually anything they want without the need to work, there is little need for laws or enforcement, and the culture is described by Banks as space
socialism."
There is a mistaken assumption that if you eliminate want, you will eliminate greed. That may be true for a large percentage of the human race, but that isn't true for all. Look at how the super rich are bifurcated.
Some are of the attitude that once you have enough to meet all your wants and needs, just having more money is pointless. Many of these people become philanthropists who give away much of their fortune, or find some way to use much of their fortune for the common good. A lot of the tech billionaires are this way, and there are a few others like Warren Buffet. Bill Gates and Warren Buffet are giving away their fortunes while Elon Musk keeps plowing his back into projects he hopes will improve humanity.
Then there are the other super rich who count their money to keep score. Some use it to see how much influence they can buy like the Koch family or Sheldon Adelson. Others flash their wealth around so the world sees them as rich like our current president. A lot of people who made big money in the financial sector essentially screwing other people out of their money are mostly in this crowd too.
It's been said that some of the most cut throat, back stabbing, game playing happens in college faculties where the rewards are relatively small.
If the entire population was effectively super rich, some percentage of the population would continue to do something to try and be "better" than their neighbor. If money was not an issue, they would fight over something else.
People like Elon Musk have a lot of trouble grokking people like the Koch brothers or Donald Trump. They are alien creatures and their motives are often ignored by those who take a more utopian view of the future. Alan Greenspan ignored the warnings about what could happen to the world economy if the people running the derivative markets were not regulated because he couldn't wrap his head around the possibility that those people would run the world's economy into a ditch for their own gains.
If you want a snapshot of what human culture would look like if everyone had all their needs and wants met, look at how the super rich behave. One Donald Trump or Koch brother unchecked could undo all the good a thousand Elon Musks do.
Unfortunately I think the Culture series is as much fantasy as Lord of the Rings. Trying to create that society without realizing what human nature really is will likely result in disaster.