Caching is a performance improvement. There is no software that requires caching, therefore it is always something being added on top of the business logic that is fundamentally required. As such, a cache is increasing complexity by nature of its existence.
The only scenario where it would simplify software is if a bunch of complex (non-cache) things are being done to improve perf, and a cache would be the simpler solution. But in that case the simplifying step is not adding a cache, it is removing complex things that aren't actually required. After that you add a cache to improve performance (which increases complexity but is worth it for this imagined use-case). But maybe you remove the complex perf shenanigans, and realize that perf is still "good enough" even without a cache, keeping your software even simpler.
The only scenario where it would simplify software is if a bunch of complex (non-cache) things are being done to improve perf, and a cache would be the simpler solution. But in that case the simplifying step is not adding a cache, it is removing complex things that aren't actually required. After that you add a cache to improve performance (which increases complexity but is worth it for this imagined use-case). But maybe you remove the complex perf shenanigans, and realize that perf is still "good enough" even without a cache, keeping your software even simpler.