As you might expect, I get this question mostly from confirmation students. And depending on the student, I often give different answers, because very often the question means different things.
As far as I'm concerned, the ultimate point of confirmation is helping the student to transition from the - often simple and trusting, if certainly not unquestioning - faith of a child, into a more complex, nuanced faith that will grow with them into adulthood and stay with them all their life. Confirmation traditionally involves three sections: focused study in the Bible, learning how it's structured and what it says; learning Martin Luther's Small Catechism, which explains Baptism, Communion, the Lord's Prayer, the Ten Commandments, the Apostle's Creed, and a few other things; and probably also a section on "Christian Life"- or how our faith is involved in our daily lives.
Those of us who are "cradle Lutherans" were likely baptized as infants or very small children- so students were probably welcomed into the family of God by others, not on their own terms. At the confirmation service, after having gone through a new level of focused education, students "confirm" their faith in front of the congregation. They take on the promises of baptism, meant to lead them into a Christian life in Christian community, as their own.
After being confirmed, students are considered adult members of the church. They can speak up during congregational meetings, they can most likely be members of various councils and committees, and often they take on more responsibility for their faith life with their families, perhaps getting more of a say in which church service they'd like to attend or what they'll volunteer for.
Whether or not those who are confirmed but under the age of 18 have a vote in congregational meetings (such as an Annual Meeting or calling a pastor) depends, to some extent, on the congregation. In the USA, my understanding is that no one under 18 is allowed to enter a "binding legal contract" that involves money- so those under 18 cannot vote on anything that involves the budget, or hiring staff (including a pastor). Some congregations do allow those under 18 to vote on things that don't involve money- which ministries to emphasize, changes to worship services, etc.
Personally speaking, I have to say I have no ethical problem with families forcing their kids to go through the confirmation classes against their will. It's education, and like any class at school they might not like, it will almost certainly come in handy down the road. Western culture has been shaped by Christianity in a lot of ways, and learning a bit more about the Bible and what the church does is very practical.
However, I cannot agree to actually confirm the student, at the confirmation service, if the student is unwilling or even just not ready yet. Participating in that service is each student's choice, and if they cannot agree to the promises they are to make at that service, I won't force them to lie about it in front of their friends and family. Any of my future students who would have questions or concerns about this will always be welcome to discuss this with me, and I will always be willing to help them and their family discuss it as well. If a student wants to put off confirmation for awhile while they consider further, or study other denominations or religions, that is always their choice to make.
A few words on something confirmation isn't: in some faiths, there's a concept of an "age of accountability"- that small children are not responsible for their actions, but once a child reaches a certain age, then they are. That's not what confirmation is. We are all equally responsible for our actions at any age - and we have each been equally forgiven by the grace of God, through the death and resurrection of Jesus Christ. Confirmation does mean claiming the faith as one's own, and it changes one's relationship with the church and the congregation, but that's all.
Confirmation may well be a little difficult or confusing, but the point, again, is to give the student resources and tools they can use for the rest of their life, as their faith grows and changes with them.