I like when people make a lot of assumptions while criticizing someone for making assumptions.
I am a diagnosed in adulthood user, diagnosed at age 20. 2 years after doing poorly in college. I actually relate to OP quite a bit. Same problems with focusing in class growing up, same problems in college. OP explained all this, I didn't make any assumptions. Typically, if you have severe ADHD, you are such an annoying child that nobody can miss it. Can't stay seated. Can't stop talking. Can't be controlled, because the low level of executive functioning just wont allow it. It doesn't sound like OP's ADHD was at that level based on his explanation.
Hyperfocus isn't a gift. It is something you have to train through practice. I didn't even experience it until after I had been diagnosed. And I developed it through reading. That does not imply that it was easy by any means. Cognitive behavioral therapy is not easy. If it was, nobody would have psychological problems. I sat and I read, and reread, the same shit over and over again, struggling to retain. I just really wanted to read Game of Thrones after watching the first season, so I didn't give up. Eventually, I started to develop my hyperfocus while reading, and now I read every day to keep building it. It is true, I am assuming that everyone can practice a and grow a skill if they try hard, but that assumption is pretty well supported by the psychology of learning. But you are assuming that they can't. At least my assumption is not completely defeatist and demoralizing.
OP has lived 19 years of his life fine without medication. Your emotional reaction to me suggesting he should try to cope without it through some cognitive behavioral therapies exposes your obvious bias. We are here to support each other with our own experiences coping. In the same paragraph that you criticize me for my supportive opinions based on my experiences and the experiences of people in my life also affected, you state your own opinion as if it is fact.
You are perpetuating the idea that medications are a 100% safe long term solution when that is not the case. Great, I'm glad it works as a quick easy solution for you right now, but that is not the case for everyone either. My cousin, age 32, had to cease use of his medications because it caused him to have heart problems. Many of these medications are also highly correlated with pulmonary disease. There's a lot of side effects to be experienced with medication so as with any medication, if you can cope without it, then you should. If you can't cope without it, by all means take it. I don't judge you. Plenty of my loves ones medicate for various disorders. OP won't know how well he can cope without it until he tries. It is my opinion that he should try, I don't see anything wrong with that.
And the caffeine thing is interesting. It makes my ADHD x10 when I drink it, my mom avoids it as well for the same reason, but we have similar genes so maybe that is just us. But maybe not, doesn't hurt OP to try without it to see if it helps. Again, just a suggestion, not a rule.
I have a background in cognitive behavioral therapy, as does my wife, which likely contributes to my success in coping without medication. That background though is just knowledge used to devise tricks for altering ADHD behavior, knowledge that I was excited to share. Though now I see that I am going to have to combat a lot of bias while I'm here.