How very human-centric of you ;)

It’s not hard to imagine a program of ever increasing complexity, highly redundant, error-prone, yet also stochastically, statically, increasingly effective.

The primary pushback from this would be our pathetically tiny short term memory. Blow that limitation up and complexity that seems incomprehensible to us becomes perfectly reasonable.

The world of Deepness in the Sky (at that time, A Fire Upon the Deep is a very different time) doesn't have AI. It has civilizations that rise and fall every few centuries. The Qeng Ho are a trading culture that was formed to try to bind the wandering traders of the universe together into something that could stifle those collapses. This is probably strongly influenced by Foundation by Asimov.

Other things are quite advanced - but computing is rather "dumb". What is there is driven by a great weight of inertia of massive software (all written by regular humans) that itself is too large to fully audit and understand.

The story it tells is very much one about humans and societies.

If you need an arbitrary point of reference to count time from, what's simpler, making a new one or using the existing predominant one that everything else does?

Making a competing standard and then having to deal with interop between standards is not simpler or better unless there's an actual benefit to be had.

Simplification is only accessible when understanding all systems are complex. Meaning, to simplify is just the ability to break down complexity into smaller parts.

We do this through categorization. For example, integrated circuits can be broken down into simplistic AND, OR, XOR, NOR, NAND, X OR, and NOt gates. Yet tying those together creates usable components such as Wifi radios and manufacturing automation.

Over simplification are concepts that lack understanding of complex systems. These are exploited by politicians. For example, deregulation will help drive the economy. Yet regulations have been proven to assist the economy long term by preventing the next variation of thalidomide. The panacea drug of the 1950s and 1960s that killed their users or caused massive birth defects.

Even smart people have an appendix!

It depends if there's anything left to simplify. Maybe this is the optimum we'll reach between concise expression and accuracy of representation.

That’s because it’s not a self-improving computer system. It’s just programming as it exists today for thousands of years.

How would something grow in complexity yet get around the fact that changes would be hard to effect at scale?

Was the sarcasm lost on me?