I’ll start:

  • RSS and blogs, news vs. social media
  • XMPP vs. WhatsApp/FB messenger/Snapchat
  • IRC vs. Matrix, Teams, Discord etc.
  • Forums vs. Social media, Reddit, Lemmy(?)
  • It’s also what creates a ton of bugs and problems, both for users and developers. People hate on Gnome for being very standard without a lot of config options, but it makes a ‘standard’ Gnome desktop possible in a way that just doesn’t exist for KDE.