Hydroelectric generation is reliable. So reliable that New York State generates approximately 70% of its electricity from hydro.
Fashionably, the state government is planning to replace every hydro plant with wind or solar over the next 20 years.
Washington State is the only one I can think of that produces that much hydro energy: https://www.eia.gov/state/index.php?sid=WA#tabs-4
but describing renewables like wind and solar is missing the whole picture.
Now I might be completely off track and putting words in the mouth of OP without any proof. Just a hunch.
The dams are not anymore as "reliable" as they used to be, not because of the construction, but because of the global evolution of the environment.
Which, it's worth noting, is also the proportion Canada's national electricity production happens to be. And of that remaining fraction, half is nuclear.
Canada has very favorable geography for hydroelectric generation to the point where they're synonyms (people will sometimes call it "the hydro" here). Having vast quantities of unproductive land on what's functionally bedrock is still sometimes useful.
Even when the dam is 70 years old?