In my experience, I agree the core functionality (variant management, remote config, etc.) is relatively small amount of effort compared to the interfaces to make it accessible to those non-technical orgs, like you mention.

However, we found that those interfaces only allow very limited, shallow tests and you very quickly outgrow them as an organization. In other words, once you reach diminishing returns on button color and header text optimizations, you start wanting to test deeper UI experiences and complicated user flows. At that point, you have to involve engineering anyway.

When an organization has engineers who are motivated by business metrics, they have no problem implementing shallow tests (like button colors) while working on tests of the deeper UI experiences as well. And at that point, the non-technical interfaces have little value.