I would honestly like to hear a better alternative. Is it fair, reasonable, or just, that some subset of society is tasked with putting their life on the line to defend everyone else? That very quickly devolves into something like the US system where people with less resources and options end up signing up out of economic necessity. Then they end up fighting and dying for a richer elite that doesn't have a skin in the game.

It's a pretty simple concept really: I'll protect my neighbours if necessary, and they'll protect me. We're in this together. The only incentive anyone should have to be in the military is to defend themselves and their (extended) neighbours.

You can make the exact same argument for taxes: Should some subset of society be taxed, while everyone gets the same social safety net and general rights? I think not: I think everyone should contribute, and that everyone should get the benefits.

As for the starship troopers comment: That society is fundamentally segregated into people with rights, and people without them. It also happens to be a heavily militaristic society. Starship Troopers shows exactly the kind of society I think looks terrible, because most soldiers there effectively sign up out of necessity, while those with resources can live peacefully. I'm advocating for equality, not segregation. I'm also trying to be explicit about saying that the only use of a military should be defensive. You could summarise this by saying that, in peacetime, we should have an absolutely minimal military, and everyone has equal rights. If the need arises, everyone has the same obligation to defend each other.