We need to get back to our roots on this site, so here's a list of reasons why Wikipedia just plain sucks.
1. Wikipedia is not an encyclopedia, it's a website -- which means it lives in an Eternal Now. Thus you have reams of abandoned projects, those silly tags on articles that are now ten-fifteen years old, and so on. Which leads to....
2. Wikipedia's new use: to catalog news stories. Anything major that comes down the pike is turned into a stub article or an extension of a pre-existing article. And those stub articles can grow into "real" ones. This goes against the encyclopedia tradition of waiting until the event is over. We've mentioned before elsewhere how the Encyclopaedia Britannica treated World War I; they issued supplementary yearbooks covering the war as it happened, then incorporated the important points in the next edition in 1928. Because the Wikipedia editing/writing pool is unpaid and voluntary, doing this is easier than filling out the lists of green algae from a Van Nostrand's Scientific Encyclopedia or some other dreckwork.
3. Speaking of dreckwork, the editor pool is shrinking (even Time mentioned it in 2016) and the remaining hard core have become administrators. The majority of work on website is now done by "software robots", ranging from writing stub articles to doing small edits ("gnoming") to fighting vandalism. Wikipedia itself seems proud that crude AI is bring harnessed in this way.
4. A large number of editors have mental problems as we pointed out seven years ago. Andrew Morrow is an example of a lot of issues (delusions, stalking, repeated arrests) in one person. He's been locked up off and on for a decade or more.
6. The culture of "article control" and Wikilawyering has ruined multiple articles, case in point the article on the Franklin Community Federal Credit Union scandal involving Lawrence E. King, Jr. has been scrambled into garbage -- the case began as an investigation into an imploding credit union in Omaha, Nebraska, then began uncovering links between King, Jr. and other prominent Omahans running a child prostitution ring that also involved Boys Town (one of the sources for the children to be abused). This was in June of 1988. By 1990 the case was dismissed as a "carefully crafted hoax" and some of the witnesses to a federal grand jury were jailed on perjury charges. The reality was that they were forced by prosecutors to claim they had created a hoax; the network seemed to go to the top of the Republican Party, and the Reagan and Bush administrations seemed desperate to bury yet another scandal after the Iran-Contra hearings. The Wikipedia article completely avoids Nick Bryant's book The Franklin Scandal: A Story of Powerbrokers, Child Abuse & Betrayal (2009) and John DeCamp's The Franklin Cover-up: Child Abuse, Satanism, and Murder in Nebraska (1992) because MONGO, Arthur Rubin, and Tom Harrison wanted it like that. Nick Bryant attempted to balance the article in 2014, and was countered by MONGO over and over again....because MONGO is a hard-core Republican. Here is Bryant's blog post on the editing fight.
7. This also brings up the problem of "Wikipedia as reality control", i.e. if it isn't mentioned in Wikipedia, it couldn't have happened. Jack M. Sell's 1980 film The Psychotronic Man gets a writeup because the term "psychotronic" was used by 'zine writer Michael J. Weldon (Psychotronic Video magazine and two film/video guides). However, you will not find a Wikipedia BLP on Jack M. Sell, nor an article on any of his other films, including Deadly Spygames (1988), which featured Tippi Hedren. However if you check Hedren's Wikipedia BLP, her filmography chart lists Deadly Spygames! The Internet Archive has a VHS transfer of Sell's Outtakes '87 (aka Outtakes!) and Sell's business website is still up, but any actual biography is only a couple of lines at IMDb. And Sell has gotten off easy -- there are tons of people and things lacking any Wikipedia existence at all, as this forum thread will show the reader.
8. WikiPedos. Enough written.