It's like comparing a pickup to a van. They're both largish cars with some storage potential, but the venn-diagram of people considering either as their personal vehicle is gonna be pretty small.
MediaWiki is a great tool, but it's not targeting Enterprise, basically.
Obviously not ready for prime-time, but might get there in due time.
Advanced macros? As far as I've used both, I never had a macro in Confluence that couldn't also be implemented in MediaWiki. You can basically have access to the whole of PHP in MediaWiki so not sure what the limitation is here.
> deep integration into Jira, bitbucket etc
I mean, obviously. Which "open source corporate wiki" could even have as deep integration with Atlassian as a Atlassian product? Atlassian would never allow you embed non-Atlassian stuff into BitBucket. Why would they allow for example GitLab to embed their issues in their own product with as deep integration?