Office
Last decent version was 2003. The Ribbon and now deleting little used but important features killed Office for me.
I never used Access or VBA or Macros (all evil) so changing from Office XP to LibreOffice was easy (do edit all the defaults).
Why does Skype now create cookies on Win10.
Why does Windows Skype have stupid "Home" screen and adverts (both removable).
Why does a new install of skype destroy your existing account profile avatar.
Why is Skype on task bar like an open program and not in Notification area like it used to be (and still is on Linux).
Why are they killing Skype Phones, Skype on embedded stuff and killing Linux skype to replace Linux version with a nastier one?
Because MS are obsessed with phones, where they have < 2% market and are determined to abuse desktop users.