This, for most cruises, is no change at all. Almost every cruise from an American port already does this. Now be honest, how many people are actually listening to the briefing? Maybe you do, but I just came back from a cruise that sailed within a week or two of the latest sinking, and looking around at the other passengers during the briefing was hillarious. Very few looked as if they were listening at all. Talking between themselves, or even to some of the crew. Some were already obviously a bit inebriated. There were some listening to the Captain, but not a very high percent.
As far as being proactive, how many cruiseships have actually sunk in the last 20 years. You could probably count them on one hand. And there was little if any loss of life until the latest (of course any death is unacceptable). Passing these rule are reactive, but how do you be proactive if the captain breaks the rules. Maybe the cruise lines should just make sure that their Captains know what they're doing. Almost all of cruiseship sinkings are from human error.
I am not against drinking, but alcohol related deaths far outnumber deaths from sinking. Maybe cruiselines should be a bit more proactive when it comes to serving passengers who are obviously drunk.