[fennecs]

Use a programming that is decoupled from stateful manipulations and control flow?

Programming does not need to involve itself with the hardware, that’s just a tool for evaluation. A program is an idea expressed in a language. It’s some formal statement of intent. Sometimes we can evaluate it to produce an output. Sometimes these statements are muddied by underlying representations.

The length of a declarative program seems a pretty good rough measure of complexity in the way you are talking about. Operational complexity of course, in the number of steps to actually evaluate it is a bit different, based on what you are using.