Why does it matter why they were built? Low carbon energy is low carbon energy, while some countries may have an natural advantage it typically tends to be in places with lower options for solar.
Perhaps, but definitely something to worry about after net zero. Dams, especially existing ones, tend to cause local damage to a handful of species, while the natural gas they take off the grid damages nearly all of the ecosystems on the planet while killing people even in normal operation.
This is blatantly untrue. Dams act like huge batteries that can be used to smoothen out the load if demand or supply drop.
It should be used in conjunction with other sustainable energy methods. Over production can be used to pump up water and if production of wind and solar drops (as they tend to). Water electricity can fill the gap.
Power grids are very complex and require great forethought and balancing options. If water energy cannot be used, nuclear is the best balancing power.
For a dam which already exists, surely keeping it in use makes more sense than decommissioning it in favour of fossil fuels though?
We probably shouldn't be building any more, but unless our grid is already completely renewable, hydro stations are the last ones we should be taking offline.