The thing about ADHD is that the “lack of reward chemicals in your brain” doesn’t just mean that you don’t want to do any tasks that don’t feel particularly yummy :(, it means that your brain will look at chores and tasks that need to be done like “doing this would be painful and tedious for absolutely nothing to gain from it, Do Not Do That.” The same thing that your brain tells you about everything else that would feel really bad and hurt the entire time that you’re dying. The part of your brain that stops you from doing the thing is the same part that keeps you from shoving your arm into a wood chipper.
With unmedicated, unmanaged ADHD, “I have to do this assignment or I fail and my life will be ruined and I die” feels like a SAW trap, every single time.