I've already ditched Music (macOS: Cog; iOS: Decoupled), I'm holding off upgrading for Photos' sake, Home on macOS is an absolute nightmare, Mail is meh but ok (fingers crossed they won't accidentally break it), and I'm hoping they will never go after Notes - it's central to so many things in my life.
Meanwhile, I'm still using Emacs, because despite its many shortcomings (mostly the legacy architecture), ELisp makes writing simple plugins simple, and the few that I use are too excellent to get me to switch.