Wouldn't the blown-up car be more complex than the non-blown-up car?
Typically I define complexity as a low probability macrostate meaning low entropy. So debris generated from the explosion has a high probability of randomly occuring, while a new car has a very low probability of randomly occuring.
Following this definition you arrive at a formal definition of complexity that is intuitive.
Imagine a tornado that randomly reconfigures everything in it's wake. The more complex something is the less likely the tornado is going to reconfigure everything into that thing. So it is very likely for a tornado to reconfigure things into debris and extremely extremely unlikely for the tornado to reconfigure everything into a brand new car. A tornado reconfiguring atoms into a car seems to be impossible but it is not, it is simply a low probability nearly impossible configuration.
Therefore the car is more complex then exploded debris.
Think about this definition because it also aligns intuitively with the effort required and technical complexity of any object. The more effort and technical complexity it has the lower chance it has of a tornado randomly reconfiguring atoms to form that object. Thus that object is more "complex".
Whatever your definition is, the quote saying complexity cannot be created or destroyed is fundamentally from any perspective usually not true. If you want to define it as simply microservices or monoliths it still doesn't make sense. Whose to say that when converting a monolith to microservices that complexity remains conserved? Likely the complexity rises or lowers a bit or a lot. Complexity doesn't remain the same even if you use informal and inexact fuzzy definitions of complexity.
Is this not a linguistic sleight of hand? There are billions of trillions of states we label with "debris" but only a few thousand we would call "car". So a specific state of debris, then, is equal in complexity to a car?
It is literally within the formal definition entropy. Debris is a high entropy macrostate, while a car occupies a lower entropy macrostate. There are less possible atomic configurations for cars then their is for debris. Each of these individual configurations of atoms is called a microstate.
A macrostate is a collection of microstates that you define. Depending on the definition you choose that definition has an associated probability. So if you choose to define macrostate as a car, you are choosing a collection of microstates that have a low probability of occuring.
The law of thermodynamics says that systems will, over time, will gain entropy meaning they naturally progress to high probability macrostates over time. So in other words, complexity is destroyed over time by specific laws of entropy.
https://en.m.wikipedia.org/wiki/Entropy_(statistical_thermod...
The reason why this occurs is straightforward. As a system evolves and randomly jiggles over time it trends towards high probability configurations like "debris" because simply that configuration has a high probability of occuring. Generally the more billions of microstates a macrostate contains the higher entropy that macrostate is.
Through logic and probability and the second law of thermodynamics we have a formal definition of complexity and we see that complexity naturally destroys itself or degrades with time.
This is the thing that confuses people about entropy. It's definition is a generality based on microstates and macrostates you choose to define yourself. It's similar to calling a function with generics in programming where you choose to define the generic at the time of the call.
But even within this generic world their are laws (traits in rust or interfaces in c++) that tell us how that generic should behave. Just like how entropy tells us that macrostates we define will always trend towards losing complexity.
The heat death of the universe is the predicted end of the universe where all complexity is inevitably lost forever. You can define that macrostate as the collection of all microstates that do not contain any form of organization.
