Where do you store the excess power and how do you replace the power generated when the wind doesn’t blow. Tidal power (unproven tech as far as I know) would be far more consistent than wind or solar.
“Excess power” - they have to have windmills on a different type of regulated connection to the grid so that it does not overload or pump too much power into the system.
“wind doesn’t blow” - when there is not enough wind or it’s calm, backup power plants (usually coal or natural gas) need to come online to keep the windmills moving at a minimum rotation and provide the power not being produced that is needed by customers. There is a lot of energy expended to fire up a coal or natural gas plant (inefficient).