For me it’s quite simple: Ubuntu/Canonical has to have ambition in the desktop again. With visibility on the official website, aimed not only at developers, but artists, gamers, average users.
It has to have either the ambition of being the best debian-based GNOME desktop, or it should adopt another DE (which I would personally feel sad about, unless it means reverting back to Unity).
Being the best GNOME desktop means: adopting the latest version of Shell and the core apps, using Gnome Software and the core apps for updates and to communicate with the notification center, and finally: offering a vanilla GNOME workflow. Theming is OK (better than Pop_OS in this regard, because Ubuntu at least respects third party apps’ official icons, save GNOME’s), but I agree with some that the default backgrounds have grown a bit stale.
Other than that, long live Ubuntu!