It feels a little clichéd to say it, but I do feel that Snow Leopard, outdated now as it is, was some kind of fortuitous confluence of factors that resulted in OS X being as close to perfect as it's ever been. Even putting aside the iOS-style elements being added, my experience has been that each version of OS X has been slightly worse than the last, and tends to introduce strange little anomalies and instabilities o…
I think you have rose colored glasses about Snow Leopard. It had plenty of bugs and hiccups. People deride the "iOS style" features of El Capitan but first, what specifically are you referring to besides Launcher? Do you think adding Notifications to OS X is bad? I find them extremely useful, and like the integration better than the spotty support Growler had among third party software. I never use Launcher but it's…
So much hideousness.
Like breaking Save As... with a clunky autosave set up.
Like a badly thought-out full screen mode that couldn't even cope with an external monitor being connected (this being something that worked on the 512k Mac).
Like automatically terminating background apps, and purging resources within apps (so that Safari would reload all your background tabs randomly).
Like App Sandboxing which is so restrictive as to rule out an entire class of applications from the piss-poor Mac App Store, and to continually fill the Console with Apple's own system services getting dinged for sandbox violations.
Like discoveryd.
Like abstracting away the filesytem, so that you hit "Move" on an document and get a crippled filepicker appearing from the title bar.
Have they actually added anything good since 10.6? Some window management has improved a bit. Startup is immensely better. iMessage is getting there (though iChat AV was still better at group video chat than anything since, including Hangouts). You mention AirDrop, but that's a mess (and the awful Chooser was still a better way of finding other Macs to connect to than the Finder is today).