Great convo, love all the details on both sides! There's shockingly little long-term study of executive dysfunction because it's so new, so I understand your dubiousness. I never read that before about neurotransmitter reuptake, but it seems plausible -- it's really hard to say. My fave AD(H)D site (low bar...) quotes a doctor saying (in 2024);

ADHD was the first disorder found to be the result of a deficiency of a specific neurotransmitter — in this case, norepinephrine — and the first disorder found to respond to medications to correct this underlying deficiency.

- https://www.additudemag.com/adhd-neuroscience-101/

But then a basic search on the actual lit paints a much murkier picture:

We found no significant differences in NET availability or regional distribution between patients with ADHD and healthy controls in all investigated brain regions (F1,41 < 0.01; P = .96). Furthermore, we identified no significant association between ADHD symptom severity and regional NET availability.

- https://pmc.ncbi.nlm.nih.gov/articles/PMC4699255/

Which is a synechdoche of the broader dynamics around the disease IMO; lots of confident people with degrees saying stuff, often while trying to sell you services or medications, but the lit is still mostly vague. The only solid finding I know about ADHD is that it lowers life expectancy... TL;DR: I wouldn't personally be so confident it's about reuptake rather than production.

To give my hot science take, I think this is a somewhat inevitable result of our differential-diagnosis-based psychiatry system. ADHD is, objectively speaking, a set of symptoms. Common sense tells us that there's some common causes in the population, sure, but treating it as a causal condition rather than a opaque descriptor leads to a lot of confusion and heartache, IMHO. Such as;

Sure, depression-induced anhedonia can result in executive dysfunction, but depression's not what ADHD is (even though ADHD can easily cause depression).

I don't have an issue with any of these specifics per-se, and I'm sure you're accurately describing your life (and mine, tbh!), but I don't believe this level of ontological separation is helpful in the longterm. Some people with depression and ADHD might have a completely different cause than people with one of either, or even than other people with both. This is why I like the 'software debugging' metaphor; it's easier to iteratively try improvements to an opaque system than it is to find the "true" cause or "real" solution. E.g.:

So far I haven't seen evidence for myself that trying harder helps. Sometimes things happen (things like trauma) that manage to keep me motivated and functional for a while, but I haven't found a working strategy to manufacture this motivation at will yet.

You're not broken for being imperfect, you're just human - I would encourage you not to let this dissuade you from pushing yourself! I consider failure-to-motivate as a cognitive event in a system with a million inputs, not a subconscious choice you made because you're broken/sinful/lazy.

In those terms, I agree with your interlocutor; regular moderate exercise can really only help, in 99% of cases. It doesn't have to fix to help :)