How much benefit does it bring to those who can't afford Internet access, let alone basic human needs?
It is as useful in health, environment, economics, education and a whole lot of other fields. Have I convinced you?
A lot of the text in that article isn't particularly actionable. The cheaper and simpler purification solutions could use more detailed information on how to construct them and where to look for available tools, materials, or devices (e.g. organizations which help distribute them, or existing things which can be repurposed). That's not really the point of Wikipedia though, especially since this some of this information needs to cater specially to each geographical area.
As for the engineer who's looking to build a water purification plant, surely the information on Wikipedia is not detailed enough to help significantly and would pale in comparison to the other resources available to someone with the means to build a plant in the first place.
- "A lot of the text in that article isn't particularly actionable" - what does this even mean? Does all of the text have to be actionable, let alone particularly so, for it to be useful?
- "...simpler purification solutions could use more detailed information on how to construct them" - no, this would not be appropriate, Wikipedia is not (yet) a detailed manual on how to do absolutely anything. But I think you implicitly admit that a good starting point has been provided.
- "...the information on Wikipedia is not detailed enough to help significantly" - yes, it is, it gives you the background, explains the jargon and provides hyperlinked references into whatever area you might need more information on. Not quite sure what your definition of "help significantly" could be here.
I will not be online for a couple of days, so if I have not convinced you, let's agree to disagree.
"Water purification" was this first thing that popped into my head based on your "basic necessities" comment earlier. The article is in fact an extremely good starting point for a competent engineer with no special knowledge of the matter. It describes the issue and outlines solutions, with linked references to further research if needed. And yes, it is detailed enough to help very significantly. I tell you this as a practising engineer with little knowledge of water purification myself. I am surprised you think otherwise.