"Critical" projects and volunteer maintainers

I've some 10 or 20 year old projects that are moderately widely used, written in languages I don't use anymore. I'm not maintaining them, and a tip jar won't entice me to do so, I have a job, and at least for ruby, the modern package tooling is so different now, I don't know how to use it.
I spent countless enjoyable hours on them, but those days are past. A couple have enough interest that I've managed to transfer maintenance to a couple other people. One should never be used again, but gets a 3million downloads a week... (no kidding). I've no idea how to get the popular upstream projects that have it as a many levels down dependency to get rid of it, and I've tried. I could just add a deprecation warning to it, so every consumer would see the warning, but that seems pretty hostile, and deleting it seems even more hostile. I really wish there was better deprecation mechanisms, and softer crowbars to get downstream consumers to move on.

I suspect that the author of the lockfile project mentioned in the article is in a similar position, unable to convince people to stop using the project, and no amount of money is going to make it easier.