Hydro ramp is very quick, only limited by the delay in mechanical inertia of the turbine and generator rotors. Most dams can be at peak output in ~10 seconds.
With that said, these particular generators can be replaced with renewables and batteries trivially (and the costs are even more reasonable with the recent passing of the inflation reduction act) due to their smallish capacity (~200 acres of land for 20MW solar, small footprint for the storage system).
Because they’re detrimental to the biome in this case. Every evaluation will be different, each with nuance.
EDIT: I think, importantly, that these decisions should require the replacement of generation capacity lost with clean generation and storage as part of the cost benefit analysis.
However, electricity is very low on the utility provided by dams. Reducing flooding and stabilizing the water supply tend to be vastly more valuable in most areas.
Both are 'the future', and both will rather dramatically increase power grid demand.
Luckily, I think 'smart' pricing and demand scheduling will mean that the infrastructure changes will be minimal and gradual despite the massively increased demand - there won't be rolling blackouts or emergencies anytime soon.
At least in WA (OR may be different but as PNW neighbors we are often pretty similar) a lot of heating locally is electric resistance, so heat pumps would actually represent a net decrease in energy use.
The value extracted from the dams was never more than a tiny fraction of just the commercial value of the fishery each eliminated, wholly leaving aside the matter of causing extinctions.
California's system with dams near peaks of the Sierra Nevada range, feeding penstocks to thousands of meters below, is both massively more efficient and causes nowhere near the ecological damage of the river valley dams being torn down.
Those were largely built in the 1920s with pulley-operated (pre-hydraulics) equipment trailered up on abysmally bad roads... that still exist, unimproved.
With that said, these particular generators can be replaced with renewables and batteries trivially (and the costs are even more reasonable with the recent passing of the inflation reduction act) due to their smallish capacity (~200 acres of land for 20MW solar, small footprint for the storage system).