You're completely right - SF is not about the future, in the same way that Narnia is not about wardrobes. It's an allegory about current society. Not trying to predict the future, but taking current trends and seeing where they go. The point is not really about guessing right or wrong, but making commentary on our current society and getting us to consider choices we may have to make.
Banks himself said that the Culture has no chance of being created by actual humans, that people would need to change in order to create it. But as a thought experiment for "what would a technological Utopia actually look like?" I think it's a very valuable contribution. There are very few Utopias that I've read about that I would actually want to live in - the Culture is probably the most attractive of any of them.
In this respect, the advent of lab-grown meat does pose the question of whether it's morally acceptable to eat animals. As far as I'm aware, only SF authors have considered this, because that's the kind of thing they do. A technological change has triggered a moral conundrum - this is the stuff that good SF ponders. It's not necessary to get the details of the technology right, or to correctly predict it. It's enough to get us thinking about this stuff before it happens.