From personal experience, many apps work suprisingly well on Phosh. The thing keeping me from using a Droidian phone with Phosh was a seemingly device-specific issue with answering regular phone calls. Kind of ironic that the linux phone could do many apps from FlatHub flawlessly with touch and everything, but not regular phone stuff. Nevertheless, the smartphone part is handled quite well with the Settings app, the quick toggles, the support for flatpaks, and so on, especially with Wayland where the android ecosystem is within reach.

If I read correctly, you identified the lack of smarthpone-level apps and distro as the limiting factor. In my opinion, the lack of sufficiently powerful but still open hardware is what we miss. Mainline linux with proper hardware support is pretty good but not complete on the Snapdragon 845, a 9 y/o platform. Anything newer? Nearly impossible without some android-specific layers (such as libhybris in the case of Droidian). Currently mid-high level hardware with PinePhone-like openness would probably let Phosh (and Plasma-Mobile, SXMO etc.) distros strive. The smart features, as in the apps, are mostly there.