It's not about gatekeeping and I agree that ADHD has different effects on everyone's life. It's about throwing it out casually and using it to pardon oneself.

All people with ADHD share the same "issues". Some more, some less. That's why you can use standardized tests to diagnose it. That's why the prescribed drugs target the same receptors in your brain. We used to differentiate between ADHD and ADD. Nowadays we combined the term and just use ADHD since both have the same issue in common: The dopaminergic system.

People should research it if they have been diagnosed. But this requires not making yourself a victim. There are many ways to coop with it and it doesn't need to rely solely on medication. But stating "I have ADHD" is a bullshit excuse to use in daily life. Take responsibility if you have been diagnosed. You can function perfectly well with ADHD - with or without medication. Anybody telling you otherwise should get lost. But it does require time and practice.