The new stuff is just better, especially if you avoid becoming an early adopter.
Sure, mechanical shifting works great and is easy to adjust when it doesn't, if you aren't mechanically inept, and is a touch lighter, but DI2 works a hair better and is even more reliable. On TT bikes the ability to shift from multiple places is a godsend.
Disc brakes work better and I don't have to fret about using swapping my deep section carbon wheels in winter time, rain, snow or whatnot.
Tubeless, now it's matured a bit? Simply brilliant.