And I know as many people who went in the opposite direction, love iOS and love the integration with their Macs (hand-off, etc.). An anecdote is just an anecdote.

At what point do people who used to be proud Apple fanatics become sheepish, and at what point do sheepish Apple users just switch to something else already?

Until 'something else' offers: good retina support (including mixing retina and non-retina displays), hardware that works out of the box, long battery life as stated by the manufacturer [1], no spying on user behavior, proper GUI and application sandboxing, low weight, uniform application look & feel + shortcuts, etc.

(I use Linux and Mac, switched from 3 years of Android back to iOS. So hardly a purist ;).)

[1] http://www.which.co.uk/news/2017/03/which-laptop-battery-tes...