Wikipedia seems to do a good job (even if not precisely specified), but I wonder why no competition has emerged at all (or has there)? Why is there no Wikipedia that allows everything?
A "Wikipedia that allows everything". Try it. It'd turn to shit really quickly.
People seem to have this idea that there was this golden age of Wikipedia where you could write everything, and then the EVIL DELETIONISTS took over. The fact is, huge amounts of what gets put up on Wikipedia is junk. Deleting it is a service to the reader in the same way anti-spam filters are to email users.
Articles need to be maintained. To be useful for readers, they have to be reasonably accurate, and in Wikipedia-land, we base accuracy on external sources. And if there aren't any external sources, how the hell can we even try and be accurate?
Fortunately, there is a solution: the rest of the web. Wikipedia has a constrained mission, namely the production of an encyclopedia. Outside Wikipedia, there is a big wide web where you can do whatever you like. Wikis that have explicit points of view, that are focussed on specific topics... all that kind of stuff.
The most common complaint I've heard was rather different: nobody questioned that some pruning is necessary but complained that the standards were incredibly arbitrary and niche interests like anime characters or minor porn stars frequently made the cut while e.g. academics were deleted because they didn't have a mainstream book, New Yorker article, etc. and the deletionist cadre wasn't interested in widely-cited papers, broad recognition within a particular field, etc.
Jason Scott also highlighted a similar problem in http://ascii.textfiles.com/archives/3826 noting that the question again has never been quality but a very small number of people deciding a topic wasn't of interest to anyone else despite demonstrated activity.
Attempting to portray this as a question of spam control or lack of external sources is either uninformed or whitewashing.
The standards aren't that arbitrary: for an article to exist, there needs to be significant coverage in multiple independent reliable sources.
Some statistics would be interesting, though. I would imagine online sources are more common in articles on recent events, and in articles on popular culture. In the area I mainly edit in (pre-20th-century history) it's almost entirely books and journal articles.
I don't understand why the developers resort to an irritating method for getting things reviewed - find the right community, know the right people, go to their court and appeal to their higher order with wonderful pitches about what should be done. There has to be a better way of dealing with things.
"If Deltionists can't cull at their whim, WP will simply end up as a pile of rubbish!"
Junk is typically not that hard to find and cull, it's the actual content that gets removed, and the absurd politics behind it, that will probably bring about the end of WP.
https://en.wikipedia.org/wiki/Wikipedia:Articles_for_deletio...
I'd love to know which of these deletions are bringing about the end of Wikipedia.
Citation needed.
Wikipedia hit a sweetspot of lots of people entering lots of information which caused it to grow rapidly.
Early deletionism and care about what could be added meant that "Random Article" was a useful link - you'd learn interesting and useful stuff from clicking it. Now, not so much. There's just so much in Wikipedia that 'Random Article" will take you to some malformed stub about a teeny tiny little thing.
Today there's a weird mix of deletionism and inclusionism. It's luck and politics if the subject you're interested in is targetted by deletionists / inclusionists. (Note that I take no sides here. Inclusionism can be just as harmful for a good Wikipedia project as deletionism.
One thing I'd like to see Wikipedia try to do better is "A lead paragraph that anyone can understand". (Perhaps linked with better efforts for Simple English Wikipedia.) Unfortunately lead paragraphs are hotly contested and thus often pretty poor.