I also think the same - a to-do app will not help. Specially if you plan to add deadline information, difficulty and value scores. These will turn into distractions themselves which will require thinking and making decisions about.
I think it's more that people who have ADHD have been gaslighted by people who insist they were just lazy. If it can be fixed with a todo app, it's "not a real illness".
There's low carb apps and there's diabetes apps. Both do essentially the same thing and yet they're almost never in the same market. Low carb is marketed as weight loss.
The other problem is that every app targeting mental health will gaslight you and call it CBT. It started with Noom. Many of them don't just feel clinical, they feel outright manipulative. Nobody wants to do a ton of surveys, but if you want something to prove successful, the only methodology they have is a ton of surveys.