That's assuming that the documentation is articulately and technically well written. Unfortunately that's more often the exception than the rule. That's rather the whole reason that StackOverflow even exists, I think.
before: questions were always open. and over time people added those details.
now, after someone answer with a one liner and gets accepted, the question is "closed to prevent 'me too' comments"
it's going downhill for the same reason every internet community does: power crazy moderators who completely misses the point of the site they moderate.
Every "me too" protected item I've seen has half a dozen "me too" answers deleted at the bottom. It's likely necessary.
This leads to a kind of popularity gold-rush pattern. Hard important stuff languishes while easy stuff is has a glut of volunteers.
I'd be interested to see what happens if questions and answers only gave up to a fixed limit of Internet-points to the authors or contributors. Would it lead to a broader knowledge base?
Yes. You're correct about that