I think I get less than 20% of my information from documentation.
For reading large sections, books or blog posts are usually more convenient.
For searching specific answers, Google and StackOverflow (or Hashnode) are usually more convenient.
The role that documentation does fill is having long lists of all options. But I don't often want to know what options are available, I usually want to know which option I need to achieve something.
DB2 and ifort stood out to me as having bad documentation.