The idea behind having the categories collapsed by default was that right now we have too many classes and functions to have them all show by default, i understand that when looking for a specific function is easier but for beginners who land in the docs page for the first time seeing the categories like that with links to each module's introduction is much more understandable. there's probably a way to remember your preference by using some kind of javascript local storage or similar so once you expand the docs they'll appear expanded the next time you visit the site.
also the repo for the site is in https://github.com/openframeworks/ofSite any contributions in that direction or a search function would be really useful