The problem with dams is that for the most part in the West all the good sites near population centers have been taken. In developing countries you have the issue of new dams potentially making older downstream ones less useful, which is now a real conflict point with Egypt vs Sudan vs Ethiopia, Afghanistan vs Iran, China vs India and SEA, etc.

In addition, because silt will back up in reservoirs there are an increasing amount of old dams where removal makes more sense than spending more money on dredging and maintaining the dam; and with droughts becoming more common hydro is not as reliable for baseload anymore.