In reply to The Pylon King:
Another point to bear in mind is that people tend to get good at those things that they spend most time doing. In the world of climbing, and across the whole population, there has been a gradual shift in the type of climbing that most people tend to do, with a resulting shift in expertise; so it's quite conceivable that climbers of several decades ago were better than modern-day climbers at some particular type of climbing that was widely practised back then but is less popular now. Cracks, for instance, in all their more obvious and awkward forms.
When climbing various upland protuberances purely for the fun of it first took hold, the routes followed by pioneers - which of course gradually became "routes" - tended to follow the more obvious lines of weakness. By and large these were the (enclosed and secure) gullies, chimneys and cracks rather than the (exposed and precarious) open faces and buttresses in between; furthermore, and when climbing ground-up onsight, it would have been generally easier to see from below whether some major fissure-line actually led anywhere, than to tell whether a fortuitous line of holds out on an open face did the same. As rudimentary ropework gradually developed the cracks and gullies would have offered more in the way of belaying potential, in the form of various wedged blocks and flakes that could be slung or threaded; unlike dolomite rock, with its myriad "clessidra" features on easier routes, the buttress- and face-climbs on our mountain and moorland crags don't offer such natural tunnel-threads in anything like the same abundance, simply the occasional slingable flake. Early climbers, therefore, became very good at climbing these fissure lines and all the features found therein - and they weren't necessarily easier than subsequent climbs out on the intervening faces, simply more obvious objectives.
When climbers started venturing out onto the open faces in search of unclimbed rock, and lacking our modern gear that often allows a face-climb on relatively featured rock to be almost as protectable as a crack, this would have involved a definite escalation in overall difficulty and would have been graded accordingly; the climbs would have been more serious, the positions more intimidating, and the required climbing techniques less familiar - although not necessarily technically any harder than than some of the earlier routes. But as such adventures became more commonplace and gear development significantly reduced the risk factor, people started to realise that many of these newer routes were actually more enjoyable than the old ones. Spool on several decades to where we are now, with bouldering and sport climbing offering the possibility of reaching a high level of technical ability while in the process completely by-passing an earlier learning ladder wherein some degree of crack-involvement was pretty much mandatory, and it's easy to see why a modern climber might find a world of difference between two old Severes like Crackstone Rib and Deer Bield Crack, or a VS like The Brain and an old one (I think) like Right Eliminate!