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 suppose I'm arguing that ADHD is an extreme of something that most people experience to a lesser degree all the time. Many will relate to these memes and assume that they have ADHD, not recognizing that these can also be normal behaviors. Kind of like how you can be sad without being clinically depressed. I think I'm an asshole for suggesting that there are people who will blame ADHD for behaviors that they are more in control of than they realize - for suggesting that ADHD is a medical condition and not merely a club that one can invite themselves into because they relate to a meme. Any sort of gatekeeping is assholish I suppose, but respectfully, that's how it looks to me.