Everyone who remembers how much better phones with slide-out keyboards were.
Commenters here seem to be focusing on the available OSes, but most flagship phones from a few years ago without a locked bootloader will run Lineage or Uubuntu Touch. FXtec's offering here is just that the bootloader won't be uncooperative.
The real killer feature is the keyboard. Those questioning the utility of a slide-out keyboard on a phone have obviously never used one. The speed and precision possible is miles ahead of an on-screen keyboard, plus there's all the extra screen real estate. While you can't touch type in the classic 4-fingers-on-home-row way, you certainly can learn to 'touch type' with your thumbs. Those who want proper touch typing can sit down in front of a Gemini, a slide-out keyboard excels at blasting out messages while standing on the metro.
There are plenty of us still holding onto our Motorola Photons and Droids (now so old the hardware is beginning to fail), blackberries (permanently locked bootloader) and Geminis (not a real phone, clamshell keyboard). For us, this is as close to the dream phone we've been waiting for as we'll likely ever see.
> swipe typing coupled with autocorrect works astonishingly well
Last I checked, AnySoftKeyboard had the only FOSS implementation of swipe typing, and it wasn't very good. All the providers of decent swiping keyboards have a profit incentive to mine your data, and a keyboard that leaks information makes any other protections redundant.