There are a whole series of problems. Darrieus turbines and their variations are fun to watch.[1] But they have structural strength problems. Also, they're hard to stop. Large bladed turbines have variable pitch, and are set to neutral during high wind conditions to prevent overspeeding. Most of the vertical designs can't do that.

In the early days of California wind power, there were some Darrieus turbines at Pacheco Pass. They're probably gone now. In those days, 30KW was a big turbine.

[1] https://en.wikipedia.org/wiki/Darrieus_wind_turbine