Sometimes the modular system is very flexible and straightforward. Other times the system really is modular, but makes many assumptions which make little sense

Sometimes the modular system is very flexible and straightforward. Other times the system really is modular, but makes many assumptions which make little sense to and are even difficult to foresee by someone less familiar with the overall system. See all the years of discussion over libraries vs frameworks vs complete code ecosystems. If I have a three week deadline and it takes three months to come up to speed with your system's docs and code, I'm going to ask for something without an up-front PR before I take it on myself.