I'm quite optimistic about a usable Linux phone in the near future, maybe 5 years from now or so. When smartphones were a new thing, it was really hard for open source projects without a major company backing them to keep up with all the new developments. Hence all the projects that died out. But innovation on smartphones has basically come to a halt these days. Sure, your phone can get a little bit faster and have round displays now, but nobody cares anymore. Nothing of all that is essential. So, give it some time, we'll get there.
I'm optimistic about the apps and desktop environments. We have made huge progress. But the problem is the hardware support. It seems that there are very few ARM SoCs, which work well with the mainline Linux kernel. So PinePhone uses a 2010 SoC and PinePhone Pro a 2016 SoC. And after all that time and despite community's efforts to upstream everything, the mainline support is still not complete and we still use custom kernels.
Yes, but that's exactly my point. The need for hardware support shrinks if the hardware doesn't change every few months. A chip from a few years ago is still very fine. That was not the case in 2009.