I'd add the additional nuance that cognitive load is highly dependent on the brain of the subject. One person's cognitive load is another person's effortless routine--it largely depends on how often the person works with those concepts and how quickly they can switch into the "mode". Where one person sees a wall of indecipherable matrix variables in Python, another person sees that it's obviously just a Cholesky decomposition as part of a Monte Carlo simulation.
So where to push the complexity should be dependent on who will be interacting with it and what they consider "cognitive load".
As an additional example:
> Rendering your web application entirely on the frontend in React, or entirely on the backend with templates, where all the logic lives in one place, is much easier than doing server-sided rendering then hydrating on the frontend.
For an expert front-end React developer, rendering entirely in the backend with Jinja templates would be higher cognitive load than the other options, even if it is technically simpler.
So where to push the complexity should be dependent on who will be interacting with it and what they consider "cognitive load".
As an additional example:
> Rendering your web application entirely on the frontend in React, or entirely on the backend with templates, where all the logic lives in one place, is much easier than doing server-sided rendering then hydrating on the frontend.
For an expert front-end React developer, rendering entirely in the backend with Jinja templates would be higher cognitive load than the other options, even if it is technically simpler.