The real world is always always VUCA. We create tight boundary conditions to at times force it to behave in ways that are other than complex but that is an unstable temporary arrangement. If our system is exhibiting simple behaviour right now, we must always be ready for it to slide into higher entropy, its natural state.
All real world systems are complex adaptive systems.
(For those of you who know Cynefin, this is a classic example of a clear system sliding quickly into chaotic, falling off that cliff that has always been in the Cynefin diagrams.)