Between global warming and humans pumping highly nutritious run-off into the oceans -- plus, quite probably, lots of other factors -- there have been significant jellyfish population booms in some waters, enough to make quite a mess of areas where humans have been fishing. And yes, our general response to a population boom in pest species has tended to be to find some way to kill them off -- introducing predators (which has its own history of problems), or trapping or poisoning or shooting.
As to whether this is a good solution or not... I haven't a clue; I don't know enough about population dynamics of the ocean food chain, and I can't judge how selective this widget really is in what it purees. And even assuming it works, I'm not sure what the release of the nutrients tied up in the jellyfish into the water will do to the population of everything else.
In a way, of course, this is another aspect of our having always assumed the oceans were too large for us to affect -- we also assumed they were too large to change much, period. But there must have been booms and busts there as on land, We may just have to accept that we don't know as much as we thought we did about what to expect, and figure out ways to adapt... and accept that in some situations we are going to be outcompeted.