It's also assuming the SO answer is less considerate of context than the documentation; this can be the case, but I find quite often good answers are quite comprehensive and explain things broadly.

thats exactly the point.

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.

The "me too" functionality is protection, not closing - registered users with a certain amount of reputation can still answer them. Similar to Wikipedia's system.

Every "me too" protected item I've seen has half a dozen "me too" answers deleted at the bottom. It's likely necessary.

I don't think it's just the moderators, there's also an incentive problem because a popular question/answer has no limits on its point-payout.

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?

I agree where things are badly documented. But look at the top tags, java and javascript are generally well-documented.

Nope, they are not particularly well documented.

I find JS is well documented on MDN, but doc writers can't possibly imagine all edge cases and interactions. A lot of these cases are "If you knew about that simple feature of instruction A and the simple feature of instruction B and how they work together then you can solve this problem".

Oh. I actually clean forgot that MDN has docs on JS, not just DOM :)

Yes. You're correct about that

Or that the docs exist in the first place.