We have a long way to go before we could change an adult's gender through their DNA. It will likely never be a perfect process, and even if it got close, an adult can't go back in time and go through puberty as their brain develops.
For now, no matter what science does, biological sex remains no matter what hormones or surgery you get. In the future, we may need to be more specific, maybe birthed biological sex? If you can get close to truly changing genders.
I think that this topic is like many in modern politics. Both sides see a few trees, and miss the forest. The root issue is gender norms, and people starting to en masse fight against them. I'm all for that. There would be far fewer trans youth if we could do a better job explaining gender, its norms, but also why it's perfectly acceptable for a girl to like working on cars, or for a boy to want to go to high tea.
We come from a long history of confining people to a narrow set of behaviors depending on gender, class, ethnicity, etc. Modern conservatives should be able to understand this, and get on board. The founding of America itself was a pushback against the societal, religious, and political norms of that day.
Instead of attacking or focusing on these extreme examples of the pushback, we should simply be more accepting of differences and unique traits among ourselves. Attacking these extreme measures like transitioning makes it seem like conservatives want to regress back to the dates when men went to war with a stick and women did all the housework.