Desalination system could produce freshwater that is cheaper than tap water::A new solar desalination system takes in saltwater and heats it with natural sunlight. The system flushes out accumulated salt, so replacement parts aren’t needed often, meaning the system could potentially produce drinking water that is cheaper than tap water.
Dress it up or call it whatever you want, but there have been horrible problems with it in the past, and nothing has been done to prevent them happening in the future. A problem is a problem regardless of what type of problem you want to categorize it is.
Let me put it in a way you might understand:
Ethical problem - Potentially no correct solution, tradeoffs likely.
Engineering problem - Smart people do maths until problem is solved.