It's too bad that my mid-2010 iMac—which still runs as well as the day I got it—will not be able to run Mojave. Fair, though; the thing is nearly eight years old.
For those whose devices will not run Mojave: do not fret; this is not the "end of the road" for your computers! Indeed, so long as Apple continues to support High Sierra (likely for two more years) your device ought not to be considered obsolete.
EDIT: and yes, while my iMac was indeed ~$2,500 back in 2010, the reality is that I have had no problems with it in eight years. Absolutely none. That to me is worth the Apple price premium. I'll gladly buy another iMac a couple years down the line.