Left behind and loving it
I am writing this on a 201- 17" MacBook Pro (DuoCore) running OSX 10.6.8. I suffered MacOS updates until finally saying 'screw this' as the updates broke my Office 2011, Adobe CS, Sibelius music notation, ProTools LE, and a number of smaller, very useful programs. Replacing all this was out of the question for this retiree, so I went back to the last installation disc I possessed and have been running like this for about two years now.
Only downside so far is the inability to stream some video. I have to use an outated version of Firefox (48.0.2) and consequently an outdated version of Flash. I do have Mohave loaded as an optional boot, but I have never really needed to go there. I keep a cheap PC laptop handy if I need to look at something the Mac won't load.
The huge plus side is the inability to stream some video. No autoplay crap (although embedded GIFs still show). I run AdBlocker, but the old OS still helps to eliminate 100% of ads on my computer (sorry, El Reg). I also still have those nice bouncing icons on a magnifying dock, a prettier Gallery mode (then Cover Flow) in Finder (I don't do videos so don't need the new view), and, really, a better experience, since Apple now designs for its iStuff leaving computer faithful behind.
Won't leave this until dead or someone comes up with a 17" laptop (glorious thing!) running Linux that supports legacy Mac software.