What lesson was learned? It seems like a weird corollary of the Streisand Effect: if you announce something's EOL, you'll get more clingy users that keep the product out of the grave, creating a drag on maintenance budgets, but, maybe, if you just stop maintaining and walk away, dependent users will either notice and switch away, or die themselves, and the death will ultimately be quicker and quieter.
(1) As an example: https://news.ycombinator.com/item?id=26168596