Not a lot. A tiny bit. They are still displaying text and a few images, and struggling to do even that (I wonder if Slack still needs 20% CPU to display an animated GIF). And yeah, slash commands are stil there.
> Go download MP3s and put them in your folders and use a command-line program to play them back.
Yes. We can play them back with Winamp which has all the bells and whistles that modern players have, for a fraction of resources.
> Software is not getting worse.
Current software struggle to do many of the same things that software of 20 years ago was already doing even though modern software has several magnitudes more resources.