Software used to be both fast and "feature rich" (relatively speaking), designed so users could "grow" and learn increasingly more of it. Now almost everything seems to have idiotically dumbed-down "flat" UIs that look simpler yet still manage to consume more resources than before.

The new Skype is a great example. Compare to something like this: https://www.microsip.org/ Yes, I know they're different protocols, but the point is that IM and audio/video call functionality doesn't need to take as much resources as Skype does.