I disagree. The worst way would be to make a blanket decision for all projects on their behalf.

This way they let the project maintainer decide.

For projects that don't get updated, it's better to leave them where they are.

For projects that are changing the maintainers can choose to delete (or move to a paid / OSS plan).

Choice is good, and giving that choice to maintainers is good.

The final act if goodness (and I'm not clear yet) is whether maintainers will be able to delete an image at some point in the future. Like say a year from now. Possibly by creating a paid account, and "reclaiming" that image.

Personally I agree that your advice to delete them may be the best option for most maintainers who have decided to leave. And they currently have the ability to do that.

Hence my assertion that your statement is incorrect.