Water is wayyy stronger than air. They were not made for electricity but they had a lot of mechanical forces. Honestly in remote places in mountainous regions, I've seen small hydropower projects with turbines the size of water mills power a whole village. Of course they only use it for lights, charging phones and batteries. But it's good enough compared to the alternative (no electricity)

It’d be wildly inefficient compared to modern windmills which churn out millions of watts. No one would do that.

Energy is energy. Turning a stone or turning a generator is still going to be the same ultimate thing, but while these and water mills were great in their day, science and engineering has improved, leading to the ability to generate more power from the same blade diameter and wind/water speed.