I agree fully with your assessment.

I'd also add: much of the culture and thinking surrounding Agile grew out of software consultancies: organizations that have the privilege of green-fielding new projects and then "abandoning" them; either because their contract was over, or there's no desire (or capital) from stakeholders to improve the software. So it doesn’t surprise me that their model breaks down for software that undergoes continuous modification for years, as that’s an atypical case for consultancies.