I’ve encountered a similar phenomenon with regard to skill as well: people want to ensure that every part of the software system can be understood and operated by the least skilled members of the team (meaning completely inexperienced people).
But similarly to personal responsibility, it’s worth asking what the costs of that approach are, and why it is that we shouldn’t have either baseline expectations of skill or shouldn’t expect that some parts of the software system require higher levels of expertise.
Did you mean something else?
Extreme B: every collegue is required to read and be able to recite x86, C specifications, postgre manual, and must have IQ 190+.
What is obscure or hard to understand is subjective.
The problem with indiscriminate application of "code has to be easy to understand" is that it can be used to make pretty much anything, including most features of your language, off limits. After all, a junior developer may not be familiar with any given feature. Thus, we can establish no reasonable lower bound on allowed complexity using such a guideline.
Conversely, what’s too simple or too difficult is very specific to the person. Somebody who’s coming to a junior developer role from a data science background might have no problem reading 200 lines of SQL. Somebody with FP background might find data transformation pipelines simple to understand but class hierarchies difficult, and so on. So the "easy to understand for anyone" guideline proves less than useful for establishing an upper bound on allowed complexity as well.
Therefore, I find that it’s more useful to talk about a lower and upper bound of what’s required and acceptable. There are things we should reasonably expect a person working on the project to know or learn (such as most language features, basic framework features, how to manipulate data, how to debug etc.) regardless of seniority. On the other hand, we don’t want to have code that’s only understood by one or two people on the team, so perhaps we say that advanced metaprogramming or category theory concepts should be applied very sparingly.
Once that competency band is established, we can work to bring everyone into the band (by providing training and support) rather than trying to stretch the band downwards to suit everyone regardless of experience.
Great point. This would also apply in the context of DEI hiring initiatives.