[2020aj]

Extensive experience writing enterprise apps in many different industries? To me it sounds like you're trying to refute a generality with anecdotal experience. Have you ever worked for a heavily regulated industry like healthcare or insurance? The business logic is heavily tied to the regulations which vary by state/country and can be quite... cumbersome.

[strictfp]

That is true. I don't really refute that there are instances of complex rulesets. I've worked in some regulated markets, but not healthcare or insurance.

That said, I stand by the point that most complexity I've seen has come from infrastructure. Because although the rulesets might be complex, the way they are encoded is usually the source of the problem IMO.

For example, if the rules of the business are encoded in such a way that unit testing them is straight-forward, it puts the business at the center.

But when every rule is testable only in a complex deployment, the complexity of the app is no longer tied to the complexity of the business.

And the latter has been more the rule than the exception in my experience.