I've spent over 20 years thinking about it, and not been able to figure it out.

Since it's clear to you, perhaps you can clarify how the Agile Manifesto applies to software product sales when there's a single developer and once-per-year product cycles?

Well, you do have a process there already — the release cycle. Why once per year?

Sure, I have a process. I have 10K+ unit tests run across multiple OSes and Python versions, I have a checklist for release, and more.

But if "a process" is all that's needed to be Agile then waterfall is Agile.

Why not once a year? Does Agile require a higher delivery frequency than that?

That is, how is your question relevant to the topic?

Individuals and interactions over processes, remember?

So, you've no real insight or commentary, and prefer to repeat proverbs.

Yeah, that's what Agile seems to mean to most people. Courtiers to the Emperor, praising the new clothes none can see.