Is this a sign of strength or weakness though? Like Wikipedia, any given topic on SO will approach “completeness”. I use stackoverflow at least as much now as in its prime - but these days just like a Wikipedia for code. I don’t consider it a flaw.
I’m sure there are topics I don’t use (the latest ML framework or the js framework du jour) where the community is still growing the database. That I use it as a mostly completed reference work just means my field/tech is mature in terms of language/frameworks
It's really hard to consider an answer to a moving target to be "complete". If the question was answered for Rails 3 but you're using Rails 5 and have the same exact question, chances are that answer isn't going to work for you. Now you have to chance that if you post the question again, is someone even paying attention? Is someone going to close your question as a duplicate? Is someone going to give you the wrong answer?
Unless you're working with a dead technology, by the time the information is "complete", it's outdated. And I would consider much of the information on SO to be just that: outdated.
It’s an interesting problem that they need to tackle. Perhaps answers should have a lifetime? Perhaps the moderation queue should include reviewing (and e.g. tagging) questions marked “rails” to be “rails-3”?
I work with the same tech I did 10 years ago - so obviously I wouldn’t want the old stuff to go away and I probably often find answers that relate to too new tech more often than the opposite
I’m sure there are topics I don’t use (the latest ML framework or the js framework du jour) where the community is still growing the database. That I use it as a mostly completed reference work just means my field/tech is mature in terms of language/frameworks