There would be some issues, e.g. I wouldn't want to see Minecraft recipes when I'm searching for "obsidian". But these seem solvable; niche articles could be flagged and downranked, or they could live in a satellite wiki project, or something else.
I remember seeing niche articles like this and enjoying it.
If, for instance, Wikipedia allowed articles on every human being, whether well-known or not, they'd likely have a larger problem than they already do with people creating attack articles against other people over extremely local disputes/feuds. With more notable people, they can look for other sources to confirm or deny information about those people.
Now what would the millions of articles about every TikTok influencer look like?
And then the same goes for products and companies. Every scam Kickstarter and onanistic startup would get a massive screed.
And then it all sits and rots forever once the academic retires, the influencer gets a real job, the Kickstarter vanishes and the startup folds, because no one else cares. But someone has to go around and fix the links and update templates and generally expend effort indefinitely.
On top of all that, while the article creator is still around, because the article is actually an advert, any attempt to edit it into a more encyclopaedic article is disproportionately likely to cause drama that burns up volunteer time and effort.
(1): One I saw recently https://en.wikipedia.org/wiki/Didier_Sornette
(2): Especially as many people actually good enough at collating and editing encyclopedic articles about subjects that aren't about their own media-based hobbies quickly decide Wikipedia isn't a very fun place to do that any more.
That cuts both ways. IMO Wikipedia has lost a lot of contributors by banning fun and disallowing the topics that people found interesting.
Not least, you can crosslink between Wikimedia sites, so you could just link to [[fans:Digimon:Whatevermon]] and have the content "nearby" in digital terms without drawing it under the same notability and sourcing guidelines as an article on benzene, say.
Which as you say would keep the (often very, perhaps to a fault) keen contributor to the fandom in the Wikimedia tent and might encourage them to contribute to Wikipedia and related sites as well.
Then again, the auxiliary Wikimedia sites are pretty neglected by the parent foundation which has more important things on its mind much of the time, mostly fundraising and finding novel ways to spend that money.
An encyclopedia excluding exhaustive videogame information is reasonable.
If you don't, you end up with 20 articles for real life fish species, and 20000 articles for fish species in videogames.
Especially since we are talking about an online encyclopedia, Wikipedia is cognizant of its biases and tries to counter them.
You mean something like Wikia?
Items can be referenced using their in-game names because there's no risk of conflict and custom templates can be created and tailored per game. Guess which one of these displays more info:
{{:Infobox:Tank}}
{{Infobox video game
| title = Factorio
| image = Factorio cover.png
| developer = Wube Software
| publisher = Wube Software
| platforms = {{cslist|[[Linux]]|[[macOS]]|[[Microsoft Windows|Windows]]|[[Nintendo Switch|Switch]]}}
| released = {{ubl|'''Linux''', '''macOS''', '''Windows'''|14 August 2020|'''Switch'''|28 October 2022}}
| genre = [[Construction and management simulation]], [[real-time strategy]]
| modes = [[Single-player]], [[multiplayer]]
| director = {{Unbulleted list|Michal Kovařík|Tomáš Kozelek|Albert Bertolín}}
| producer =
| designer = Michal Kovařík
| artist = {{Unbulleted list|Albert Bertolin|Václav Benč}}
| composer = Daniel James Taylor<br>Petr Wajsar <small>(Space Age expansion)</small>
}}
Keeping the information up-to-date is a big task for a fast-moving game. Imagine editing the card every time the dev changes the hp of the tank. The Factorio blog describes the benefits of this better than I can:
> Together with scripts, templates allow us to partially automate updating the wiki to the newest version, and alongside access to the game's source code, it is possible for me to update the wiki to a new version within a few minutes
The blog post has a lot of other interesting stuff in there as well:
https://factorio.com/blog/post/fff-233
A whole lot of work goes into making game wikis pleasant. I'm sure you could duplicate this all on Wikipedia as well, but that's a lot of additional work and communities already struggle to keep their Fandom wiki's up-to-date. The old Factorio wiki does not even have an article for the tank which has been in the game for years:
https://factorio.fandom.com/wiki/Combat
Out of date info is wrong info.
Did you purposefully pick one of the items that has an in-game naming conflict and a disambiguation line?
Being focused to a single game means there's only a few conflicts, but it's not zero.