Well, you can compare it to a current Scalpel.
Far and away the biggest change to trail bikes has been "long low slack" chassis which goes along with dropper posts and puts the rider more "in" than "on" the bike when standing on the pedals. XC bikes are not immune, but play it more conservative than trail or enduro bikes, and droppers are not yet endemic. This goes along with a different style of riding, as you might imagine. The fit is now designed for the standing position, hence the long top tubes and short stems and slacker head tubes. The seated position becomes a compromise, hence the straighter seat tubes. This hasn't ended or stabilized yet. This is most obvious looking at the distance from the pedal arm to the wheel, the new bike is maybe a couple inches longer in front.
1x on full suspension bikes prevents the line of chain tension from going all over the map as it used to allowing designers to really dial in the anti-squat. Designs prior to this were trying to find the best balance between the rings, it looks like the 2012 system was optimized around the 26t ring. For 2021, instead of being full carbon flexure, it uses the flexible stays in much the same spot as the rear pivot of a Horst link, so the chain run can intersect the main pivot. This is a little contrast to most XC bikes that are flexing in the chain stay side of the triangle. But honestly neither of these bikes looks all that great in this regard.
Other changes... boost spacing and 1x allowed for wider set pivot bearings, for a stiffer rear. Tires are generally a little bigger. A new bike would still be in warranty. The new bike looks like it will fit two bottles, not sure about the old one.