GLP-1 pharma intervention is breadboarding the human, next step is a permanent fix. Adversarial bioengineering, if you will.
Regarding your proposed gene therapy, would this gene therapy be available to anyone? Could it be refused? Is it reversible? Who would pay for it? The beauty of The Culture is that it is not monolithic, has no border, has godlike AI that takes care of all the problems, and can be abandoned or joined by anyone.