Earlier quoted context omitted.
What do you hate about iOS10? The new Messages app annoys me, but otherwise it seems fine.
Messages is too busy now, there's too much going on in that app. It's a mess of sharing options and emoji.
There are now so many garbage features, tangential to the core purpose of the app — self-deleting audio blips if you move the phone this way, internet GIF search if you swipe that way, weird drawing pad, stupid variable-location popup to add "HA HA HA" animation, recently-played music grid, full-screen-or-sometimes-not fingerpainting applet, image editor, heartbeat monitor, fucking kiss simulator (what the fuck), and I know from sorry experience (usually when trying to send a message with one hand while carrying something heavy and awkward) that there's more shit buried in here that I can't even figure out how to navigate to right now, like a signature editor — that I have had to help my dad, my wife, and my kids figure out how to get back to where send a fucking message with it, repeatedly.
You could use iOS 10 Messages to create a 6-episode TV miniseries called Software Design Gone Horribly Fucking Wrong and surely win an Emmy award for best documentary.