This is no way disregards the difficulty of living with an actually severe case of ADHD but is not what most of these people are dealing with.
EDIT: many seem to have misunderstood what I mean by this. I'm not saying these people are only claiming to have ADHD to use it as an excuse. What I mean, is that they may very well do have, and they're using it as an excuse. Mostly to themselves.
You sound like someone with ADHD who has been made feel inadequate, told they don't have it, and are continuing the cycle of shaming for something outside your control.