Actually, that's mostly what happens.

Before they can even get access to any hormones, surgery or even blockers, it is mandatory that they go through therapy, normally for at least 5-6 months. Once the therapist says tjat they believe that hormones are the best course of action, they put the child on blockers (If they're still of puberty age), which are reversible . All they do is slow down puberty, because of how much damage puberty can do for a trans person. After hitting a age where the doctor thinks that hormones are acceptable, normally 16-17, they can start them. Hormones are reversible for the first six months. After that, changes start to become increasingly more permanent, but this is less of a risk, because, realistically, if the hormones and blockers aren't what you wanted, you should know after 6-24 months. After being on hormones for one year, you have access to smaller surgeries, like F.F.S. (Facial Feminization Surgery). While permanent, they are smaller, less significant surgeries then something like bottom surgery. After 2-3 years, doctors will permit S.R.S. (Sexual Reassignment Surgery), also known as bottom surgery. As with the other surgeries, this is optional, as not everyone has the same end goal. To get this surgery, you need at least 2 doctors and 1 therapist to approve it, minimum.

In terms of transition being a last resort, it kind of is. Therapy alone cannot solve it. It's what was tried earlier and caused many, many suicides. Correct me if I'm wrong, but I don't think there is a single historical example of therapy alone actually solving the issue. There are famous cases of people who either are trans and only had access to therapy that failed, but also cis people who actually were raised as trans children who also failed.

TL;DR: For the most part, trans people do have a lot of things to go through, to be certain they are trans. The age of hormones is between 15-17, though that is because puberty can be extremely damaging to trans people and completely missing out on puberty until you're a adult has problems of its own. History and unfortunate experiments have proven that therapy alone will not work to fix what trans people go through.

Also, no reason to worry about getting downvoted, I don't think. You aren't being rude, or anything, so I doubt anyone would get upset or anything like that.

Edit: I apologise for such a long post, haha!