Marvel movies from the last 10 years are tailor-made for people with ADHD. The pacing of those movies are pretty consistent, for the most part they stick to the "A" plot, and the action is easy to follow.

For a movie that is less exploding colors, and more thoughtful, I think Memento will hold your attention. Each scene in Memento is like a mini-story that leaves you curious to see where it leads next, and into the next, and into the next. It has a manageable runtime and I think your astuteness will be rewarding.