Longhair (sorry missed your name hon),
This seems to be an issue almost every trans person works through near the beginning - 'why did I wait so long?' 'if only I had done or known X, Y, Z, I would have transitioned so much earlier!' And it strikes at every age. I felt that way at 27. Others feel that way at 20, 30, 40, 50, 60, 70 and beyond. Some even feel that way at 16. It's a sense of loss. A lost childhood as your right gender, lost teen years, lost time, etc. Even someone transitioning pre-puberty has lost time. Sure, she has a lot to look forward to, but there are still a lot of things that will never be the same. So much development and socialization happens in the first years. She's still not going to grow up the same as a cis girl.
A lot of times there's an underlying self-blame element to this. I think that's what makes it so difficult to get past for some. When you look in the mirror at the 'male features' you're afraid can't be fixed, what do you feel? Hopelessness? Regret? Is there self-blame in there? For what? Not transitioning as a kid? Not somehow stopping the T poisoning?
If you were a cis woman with these features, would you feel the same way? You may not be happy with those features, but would you blame yourself? What if as a cis woman, you found out at 21 that your masculinized features were a result of a rare condition that could have been prevented if treated in childhood? Would you blame yourself for not magically knowing? What if you did know, but the treatment was insanely expensive and your parents couldn't or wouldn't pay for it? If a cis friend had this experience, would you think it was her fault? Would you feel it's too bad for her, she could have been 'fixed' but missed her chance? Or would you encourage her to make the best of her situation now?
Longhair, yes there are trans children who are lucky to avoid the effects of puberty. But that's not you. For whatever reason, you weren't meant to transition then. You were put on this earth in a specific time and place with specific circumstances. Focusing on this is little different to focusing on why you weren't born the queen of England. It would have been nice, but that's not the way it happened. And I know this doesn't help much, but right now there are tons of trans women who would kill to be transitioning at your age and with your hair.