I beat all of the standard "ADHD isn't real" comments this time. Let's see if I can preempt them all in one go: No, just because you were misdiagnosed doesn't mean it's not real. No, just because you were on medication throughout high school and don't need it now doesn't mean it's fake. Yes, telling someone they just need to try harder, need discipline or were spoiled as a child is not unlike telling a person with depression to "cheer up".
ADHD isn't an issue with attentiveness, it's a disorder of motivation, time sense and impulse control. Everyone thinks it's a bunch of lazy people making an excuse to play video games all day but that's just a possible consequence. Given the choice between literally doing nothing while staring at a blank screen and doing something you don't want to do you'll need to fight yourself to the point of exhaustion just to do it. Your conscious self is essentially not in charge. Your most reliable tool to motivate yourself is fear. ADHD isn't some kind of vacation from responsibility, it's a nightmare.