If it doesn't run on MediaWiki, I'm not into it.
The main thing I'm worried about with other wiki software (including Wiki.js) is that if it's compatible with gadgets, userscripts and all of the other neat tools already available.
It doesn't have to be MediaWiki, or even a distant relative of it. It just has to work with them.
I will be happy if this Wiki.js platform does have compatibility with these features, though.
It is unclear to ne if you refer to statistics or gut feeling here. Would you mind clarifying?
- Wikimedia
- FANDOM
- Gamepedia
- Miraheze
FANDOM is the most massive wiki farm with over 360,000+ (as of 2016) wikis[1], which I'd give at lowest an estimate of 60% of the total number of wikis on the net, and is 88th on the Alexa rankings.[2] FANDOM is a wiki powerhouse, and you bet it uses MediaWiki.
Excluding WikiHow, I have never seen a wiki not use MediaWiki. As one of the guys that hops across many different wikis and wiki farms doing automated work, I cannot stress this enough.
[1] Brandon Rhea, FANDOM VP of Growth https://community.fandom.com/wiki/Choosing_Fandom?diff=next&... (dated June 14, 2016)
[2] Alexa.com https://www.alexa.com/siteinfo/fandom.com#section_traffic (dated ~21 July 2020)
WikiHow is using mediawiki (or at least a fork of it) https://src.wikihow.com/
But there certainly exist other wikis and wiki-like projects that dont. MDN and OWASP wiki are prominent examples that moved away from mediawiki. I think mediawiki has most of the mass-collabotation market, but there is much more competition in the open-source project documentation niche (which people often use wikis for) and corporate knowledge base market.
P.s. for the interested, mediawiki has statistics at https://pingback.wmflabs.org/#unique-wiki-count (opt-in) and https://wikiapiary.com/wiki/Main_Page (based on web crawling)