That is hilariously wrong. There’s no “right” way for an ecosystem to be. A hydro dam changes the landscape and the ecosystem re-adapts. Natural dams form all the time in nature as well, should we go around breaking these up to “save” the ecosystem?
Well no, building a dam fully destroys a valley's ecosystem. A point of comparison: Chernobyl also has a new ecosystem around it, where re-adaptation has occurred. We know the radioactivity is too high around it for a 21st century's human lifespan of ~80 years.
Boars and birds are having a ball. Does it not follow that your accepting the environmental damage from a dam means also that you accept the environmental damage from an early generation fission clusterfuck?
Some of the dams affect a wider area than the Chernobyl exclusion zone.
Ok, does that mean that we should drain the Great Lakes so we can "restore" them as valleys with their own ecosystem? (supposing that we could make them off limits to building, so Chicago and Gary and other cities on what are now lakes couldn't encroach; and never mind that we don't know what they were like before the glaciers carved them out, or if they were even valleys back then) Would that be better in some objective way?