> I've always been one to 'just deal with it' but after a few years of working through school and seeing my younger brothers go through the same thing with medication, I realized that I was essentially just handicapping myself.
That's not entirely true, though. There is a lot of value in learning good habits to cope with ADHD and developing systems and mental models to improve your ADHD situation. ADHD isn't a purely dopaminergic "chemical imbalance" in the brain that can only be improved with chemical solutions, similar to how depression isn't entirely a chemical imbalance of serotonin.
One of the downsides of aggressive ADHD medication treatment is that it can handicap learning of good habits and coping strategies. Some, thought not all, patients quickly learn to rely on the stimulant effect of their medication to get anything done, assuming that medication is the only way to improve. This becomes a problem as the motivating effects of stimulant medication wear off after months or years, leaving only the concentration-enhancing side effects. Internet forums are full of 20-something ADHD patients who think the only way to address their ADHD is ever increasing doses of stimulants, but eventually they hit prescribing limits and increasing side effects. The solution is to approach ADHD as a combined treatment with minimal medication and heavy emphasis on self-discipline and healthy habits.
Regarding this study: Don't forget that ADHD medications aren't simply dopamine dispensers. All of the stimulant ADHD medications have significant norepinephrine activity, as well. There are many reasons why pure dopamine agonists aren't effective for ADHD.
> I wonder how different things would've been for me if I had started taking an effective medication at 16 and not at 25.
In reality, you may have benefited greatly by spending your formative years teaching yourself coping mechanisms and learning good study habits before introducing ADHD medication.
Many people take stimulant treatment for years or decades, but the unfortunate reality is that the long-term effectiveness of stimulants isn't exactly a sure thing. Clinical trials and studies rarely run for more than a few months. The studies on long-term patients are mixed, but not encourage for long-term effectiveness of stimulants ( https://pubmed.ncbi.nlm.nih.gov/11322742/ ). If you only recently started taking stimulants, you might be in somewhat of a "honeymoon phase" where the core effects are still strong. Note that after years of use, people will tend to overestimate the effects of the drug due to the severity of withdrawal symptoms on days off.
In short, I'd encourage you to continue addressing your ADHD symptoms with ever-improving self discipline, personal habits, and healthy lifestyle choices. The medication is part of a treatment regimen, but it shouldn't be the entirety of one's treatment regimen.