Stimulants do tend to work differently on people with ADHD than on the general population. It's mostly due to executive dysfunction which is largely exacerbated by poor regulation of dopamine/norepinephrine signaling. When you add stimulants, the signal to noise ratio improves and the dopamine baseline looks more typical. This is a great help in getting a brain to act on intentions.
In a typical person, these pathways are working well enough already. Add stimulants and the dopamine baseline is simply raised, more than it should be, which is problematic. What goes up must come down, and low dopamine feels bad. It's also a high risk place to be if you feel like the stimulant will fix it (and it will, temporarily). That's where addiction comes in.
Stimulants do effect everyone differently though. They don't help some people with ADHD. There's no single universal solution.
Regardless, if you are struggling with ADHD, I would recommend going on youtube and looking at videos by a guy named Russell Barkley. He's got a bunch and wow did I feel seen after watching a few of them.
ADHD: Essential Ideas for Parents - Dr. Russell Barkley https://www.youtube.com/watch?v=YSfCdBBqNXY
¹ https://en.wikipedia.org/wiki/Gabor_Mat%C3%A9
"This is how you treat ADHD based off science, Dr Russell Barkley part of 2012 Burnett Lecture" https://www.youtube.com/watch?v=_tpB-B8BXk0
Edit: here's a newer one by the same speaker "ADHD as Motivation Deficit Disorder" https://www.youtube.com/watch?v=bR3RJU6838c
