Fun social psych fact: research has shown group brainstorming to be an overall process loss. You're better off brainstorming alone and bringing your ideas to the table individually, ADHD or otherwise.
Lots of reasons why, but you can imagine some of the obvious ones, like only one person being able to speak at once, or groupthink issues where a person or group dominates the process.
Seeing CA propositions get rigged with misinformation and tricky language suggests to me that direct democracy might also not work without proper safeguards.