Defense indudstry in most countries is under 5% of all employees I'm pretty sure. And we also kinda need weapons to defend ourselves. Maybe you don't, but if Russia sends bombers here, it'd take a whole 5-10 minutes to reach my house from the moment they exit Russian airspace.

If anything, I think we should do away with the entertainment industry, liberal arts, etc. If anyone wants to produce art in their spare time that's fine, but everyone under 75 should be forced to work a real job. We could also mostly get rid of the auto industry since old people shouldn't be allowed to drive anyway so that's a good thing, but then that doesn't exist in most countries either so it's not really a great place for cutbacks in most of them.

I also propose cutting back on doctors and nurses in fields that disproportionately affect older people. Great way to reduce the burden on society.

OR we can just start slashing the social safety nets now. I'm paying into the national pension of the current old people now, but there are going to be no young people to pay my generation's. They're already raising the retirement age, but they'll have to start raising it faster.