The word "just" in their post may be prickly. Also, it's not really a graph search as stated, just a "choose the airport with the lowest weight". That, in theory, chooses the airport to land at, but not... the rest of it.

Yes, choosing a route would be essentially a graph search, with weather at intermediate nodes adding to edge weights, etc, but even after you've computed a target path, you're going to be continually refining that path (e.g. the thunderstorm moves in a way you didn't predict). And... flying the aircraft itself.

Autopilot in straight & level flight isn't too big of a deal. Autopilot tracking a path is doable (including ascent/decent). Auto-throttle is common on larger airliners but not in GA aircraft. Automatically configuring landing gear and flaps, as appropriate for weather conditions, is (afaik) not done automatically even in commercial airliners. And doing all of this, reliably, with the assumption that the pilot is incapacitated... that's friggin' cool!