Stack Exchange solves to a good extent the use cases:

I have a very specific question, type it on Google, find top answers
I have an answer, and I put it here because it has a much greater chance of being found due to the larger PageRank than my personal web page will ever have

points of view. It is a big open question if we can actually substantially improve it.

Major shortcoming are mentioned at idiotic Stack Overflow policies:

Scope restrictions can lead to a lot of content deletion: closing questions as off-topic
This greatly discourages new users, who might still have added value to the project.
On our website, anyone can post anything that is legal in a given country. No one can ever delete your content if it is legal, no matter their reputation.
Although you can answer your own question, there's no way to write an organized multi-page book with Stack Exchange due to shortcomings such as no table of contents, 30k max chars on answer, huge risk of deletion due to "too broad"
Absolutely no algorithmic attempt to overcome the fastest gun in the West problem (early answers have huge advantage over newer ones): meta.stackoverflow.com/questions/404535/closing-an-old-upvoted-question-as-duplicate-of-new-unvoted-questions/404567#404567
Native reputation system:
- if the living ultimate God of C++ upvotes you, you get 10 reputation
- if the first-day newb of Java upvotes you, you also get 10 reputation
Randomly split between sites like Stack Overflow vs Super User, with separate user reputations, but huge overlaps, and many questions that appears as dupes on both and never get merged.
Possible edit wars, just like Wikipedia, but these are much less common since content ownership is much clearer than in Wikipedia however

Bibliography:

Ancestors

Stack Exchange