RTGs aren’t used for power in earth orbit, because of the danger of releasing the radioactive contents on deorbit and because there’s enough sunlight here to make solar a much better option (lighter, cheaper).
RTGs are mostly used for the outer solar system where the sun is too dim to be useful.
The biggest lesson from thermodynamics is that there’s no such thing as a free lunch. We may only be taking a minuscule fraction of the wind energy, but taken to an extreme there are bound to be some bad effects. In between those extremes, there are likely less predictable effects like disruption to local wind patterns.
I doubt we’re anywhere near that and there’s probably little chance of ever getting close to that without huge jet stream harvesting generators or turbines covering most of the land, but we can’t pretend that the energy is free and completely without side-effects.