Dams are more important than they were in decades past. Existing dams are by far the easiest and cheapest source of on-demand peaking power. 10GW that you're not doing anything with, can provide load balancing for 20GW-50GW of wind and solar somewhere else. Perhaps half the country away and in a different grid entirely through the use of HVDC transmission lines.
That's not to say that the ecological consideration is nonexistent. It's not that difficult to build dams that make small sacrifices in cost and throughput to permit fish navigation. We just didn't care about that _at all_ a hundred years ago.
How come the reservoirs have significant greenhouse gas emissions? I did a curious and googled it, it looks like the reservoirs have a lot of dissolved co2 and methane (probably from natural decomposition?) but it's released when the water is churned through the turbines and spillways. Never really considered that, but then, wouldn't that also happen naturally with lakes and rivers?
Anyway the article I read says they're looking into capturing it somehow, which would reduce the emissions a bit.
Hydroelectric is not green, has a limited service life and even has significant greenhouse gas emissions from its reservoirs.
Go troll somewhere else.