This is junk science you're repeating. There's no validity in claim people who have adhd don't experience euphoria. Some people get more euphoric than others, adhd symptoms or not and surprise stimulants make people more productive.
The idea that you think people with ADHD are just normal people who have trouble focusing are missing it by a mile. Caffine makes me sleepy.
Like it doesn't make you happy. That's silly. If the only issue with me doing menial tasks was that it made me unhappy I would be so much better off because at least I would be able to do the task.