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.
I feel like an asshole for saying this but I tend to agree. I relate to every meme/post about ADHD I've ever seen, and most people I know do as well, so either we all have ADHD or, more likely, it's being misrepresented.