It's been an issue since before it was the latest stable version, and if the packages needed that version they should be declaring dependencies on it. And project.el is still today marked experimental, so this will probably happen again.
Version management in Emacs is hard but a) lots of the community runs Emacs versions much older than 1y old and at least few years of compatibility is (used to be?) a strong cultural norm, b) it's common to offer fallbacks to e.g. `locate-dominating-file` or similar primitive cases especially when using relatively new features, c) I don't think project.el is very good in general.
Version management in Emacs is hard but a) lots of the community runs Emacs versions much older than 1y old and at least few years of compatibility is (used to be?) a strong cultural norm, b) it's common to offer fallbacks to e.g. `locate-dominating-file` or similar primitive cases especially when using relatively new features, c) I don't think project.el is very good in general.