I don't blame DARPA here for trying to figure out effective defenses against these massive hurricanes, especially now as they're here to stay even if we went zero emissions today. Stopping big oil is probably outside the purview of DARPA. However, yes, stopping the fossil fuel industry is ultimately what should be being done by the government as a whole.
Being vegan, ironically one of my first thoughts about this headline was whether it's unethical exploitation of animals, so I'll weigh in:
Bivalves have very rudimentary nerve nets, making it questionable if they feel pain (I still don't eat them because humans have a habit of walking back that line for less and less cognitively complex animals, and there is at least some existing evidence of a pain response), let alone have more complex feelings.
Bivalves tend to be good for the quality of surrounding waters.
I think it's worth assigning more moral consideration to the orders of magnitude more animals whose suffering is prevented by dampening these intense storms.
Considering what pollution is doing in regards to ocean acidification and killing oysters in Mass I don't think this solution is exactly a step away from climate change as a problem.