I often work with parents and spouses of people with ADHD and so many times I will hear them say, "If they would just apply themselves! If they would just try harder!"
It's very hard for "neuro-typicals" to understand that the very part of the brain that tries harder and applies effort is the part that isn't working so well in a person who has ADHD. It's a lot like telling a person who has bad eyesight, "If you would only see better!"
That doesn't mean the person with ADHD gets a pass on getting things done. It simply means they have to use tools to help, like the person with poor eyesight uses glasses.