How do you mean? If there’s a repeated pattern that is hand written al over the place without people realizing it (or not making sense within the local context to build something more general), centralizing that pattern certainly destroys complexity, does it not? The pattern existed before and after but the centralization means you have only 1 instance of this pattern.
That wasn't complexity, it was repetition or verbosity. It's tedious to manage rather than complex.
In making it DRY you have introduced a dependency for all of the usages of that snippet of code, and made it harder to have individual uses deviate if they need to.
Of course that might be exactly what you want! It's just good to be aware that code reuse is adding complexity by way of adding a new system to manage.
A little function, no big deal. But if you find yourself writing models and extending classes just to save yourself a couple of repetitions you may have jumped off the deep end!
You now have to integrate that pattern/module, and learn/work with the tooling to integrate the pattern/module, which adds new complexity and constraints on top of the now-centralized hidden complexity.
On the whole, it’s worth it - building on the shoulders of giants lets us achieve great things with what used to require out-of-reach amount of resources.
But as a result our work has shifted towards more integration and tooling (everything from node/npm to cloud services, orchestration, containers, and ML/AI) and total complexity keeps marching on upwards.
