Compared to MediaWiki, DokuWiki is "simpler" all around and more lightweight. Simpler in visual design, simpler in how data is stored, simpler in most regards.

But in practical use, they are actually pretty close in many ways. DokuWiki is almost like a thoughtfully pared-down (from the start) MediaWiki-like wiki system.

DokuWiki still sticks pretty closely to normative wiki conventions about how a wiki "should" (is expected to) work (a la MediaWiki or maybe even as far back as WikiWikiWeb). Visit a non-existing address allows to create a new page; pages use some succinct syntax (which maybe can be replaced for Markdown using some plugin); pages look just fine on web or mobile; etc.

Also, the stored data of MediaWiki is arguably more immediately portable (and perhaps more immediately accessible just after a disaster, so long as there was a backup), since it is just a hierarchy of text files. There is no database to administrate in DokuWiki.

Granted, MediaWiki is a de facto standard. But this does not make it the only sane choice.

If you spin up and make some content in 2 or 3 different wikis, you will see that they have different strengths and weaknesses. There are a lot of interesting and great wiki systems. MediaWiki and DokuWiki are among the greats. There are obviously others, too, and people love different ones, which is wonderful. The more the better.

Some a fair-ish comparisons seem to be at https://www.wikimatrix.org/compare/dokuwiki+mediawiki and https://en.wikipedia.org/wiki/Comparison_of_wiki_software