Betz' law is not a restriction. The challenge isn't extraction of more of the energy. The challenges are:

* Production cost $ * Production cost in terms of resources (e.g. renewable organic materials vs metal, rare earth etc.) * Maintenance $ * Complexity of maintenance * Necessary area / turbine * Necessary area / turbine * Necessary volume / turbine * Noise level * Usability in extreme environmental conditions

... and maybe other things I've missed.

That's still a big restriction, other technologies could have a breakthrough which makes them 10x more efficient, this will never happen with wind turbines.

We're talking about harnessing wind power. There is no "10x more efficient".

I don't like them, where I live we had a view like something from the sound of music and now we have 8 turbines in the foreground. Also they are visible from so far away that they have diminished the perceived scale of the landscape.