If half is wasted and half is used to kill people abroad, how are they building roads, schooling children, and killing people domestically?
As soon as you get over that sort of hyperbolic cynicism, you may recognize that communities, through democracy, provide for such services as are necessary for a functioning society using taxes.
No, there’s no opt-out, as it’s impossible to stop you from ever using any of the amenities that come with the package that is “living in society”. If you are American, there are dozens of countries that will allow you to immigrate with relative ease if you believe they provide a better deal or have limited government in the way you envision.
If there are none to your liking, that’s maybe a clue that yours isn’t all that bad. There are many comparisons, across industries and countries, that allow you us to come up with a reasonable floor for the costs of providing some specific service. And western democratic governments, contrary to popular and tired complaints, do rather well.