Maybe it's because I have an older iOS device running 6.1, but the insane size of some of these sites combined with all the side-loaded javascript and CSS rendering (and re-rendering) is just making sites completely unusable.
How come I can load Metafilter in 3 seconds, but Wired takes over a minute, if it works at all? And Medium? Even worse.
OMG this. It's insanely frustrating that 90% of the time we're just reading text and it's so painful on older mobile devices that still should run circles around computers that happily consumed internet content ~10 years ago.
As the border between mobile/portable devices and dektops/workstations keeps getting blurrier, this "on mobile" concept will probably just lose any sense in the near future.