You opt into it by living in society. If you don’t want to pay taxes, find yourself a cave in the woods. If you use the roads to get to work, then you need to pay for the roads. (This applies to all public things, like if you want an educated populace, you need to pay for schools, even if you aren’t going to the school yourself. Taxes is a way to pay for all this stuff)
In most countries, living in a cave in the woods would imply trespassing or poaching. There really is no way to opt out. Arguably, that’s okay, whoever said you never have to do stuff you don’t want to was lying.
You opt into it by living in society. If you don’t want to pay taxes, find yourself a cave in the woods. If you use the roads to get to work, then you need to pay for the roads. (This applies to all public things, like if you want an educated populace, you need to pay for schools, even if you aren’t going to the school yourself. Taxes is a way to pay for all this stuff)
In most countries, living in a cave in the woods would imply trespassing or poaching. There really is no way to opt out. Arguably, that’s okay, whoever said you never have to do stuff you don’t want to was lying.