Too silly to address.
> Wikipedia's medical information is unreliable and dangerous.
Wikipedia is an encyclopaedia not a DIY medical textbook. If you see dangerous information please feel free to edit it out — Wikipedia emphatically does not give medical advice (https://en.wikipedia.org/wiki/Wikipedia:Medical_disclaimer).
> The wiki layout is useless for certain content types, such as video.
New-ish media viewer allows video playback fullscreen or inline, it's no youtube but unclear in which way you consider this useless.
> So giving free access to Wikipedia, over other sites is not actually in the public good at all. The answer is more competition.
Firstly Wikipedia Zero does not preclude, and indeed hasn't precluded, Facebook zero etc. Regarding competition, you know Wikipedia is CC-BY-SA right? You and everyone else has a right to fork the entire project, along with the mediawiki software...