The article isn't about IV being ineffective, rehydration IV are absolutely effective.
The article is about them being unnecessary unless absolutely humongous amounts of rehydration are necessary (emergency rehydration), "modern" oral rehydration is amply sufficient, cheaper, simpler, and less risky (ORS requires clean water but IV requires aseptic fluid and procedure and even then there's a risk of infection).
The article is about them being unnecessary unless absolutely humongous amounts of rehydration are necessary (emergency rehydration), "modern" oral rehydration is amply sufficient, cheaper, simpler, and less risky (ORS requires clean water but IV requires aseptic fluid and procedure and even then there's a risk of infection).