Tom, if a sub-530 yard par 5 was reachable for a low-handicapper on a downwind day, I'd say with modern equipment the same hole with an extra 40 yards tacked on ought to be reachable for him today. Between the ball, the driver, and improved metal woods that seems plausible to me. Maybe its not the SAME low-handicapper, because he's 25 years older, but someone who was equally skillful compared to average golfers of the time. When I played in the 80s on an design from that time I usually found one par 5 quite reachable, one or two more that could be (but generally weren't) depending on the wind and ground and quality of my shots, and one where there was just no way. I find the same today with modern designs. They are longer, but so am I.
The issue I have with modern par 5s is not really the length, but the drive to make the second shot "interesting". The second shots are way too interesting when you have to dodge water, sand, trees or a combination of those. Older par 5s (say pre 1960s) used to use a cross bunker, you could attempt to clear the bunker (or perhaps small cluster of bunkers) or take a narrow gap to one side or the other, and secure a short shot even if you couldn't reach the green. It was a fair risk reward proposition, and you didn't give up a huge amount of distance if you decided not to challenge it.
I see a lot of more modern courses where the landscape from 50 to 120 or more yards from the green is a veritable minefield of disasters waiting to happen. I think this came about when golfers started to be taught to lay back to their full wedge distance - if architects defended the area 60 yards out like they used to, they'd leave golfers able to lay back to the distance they were told they should be, undefended. The horror! (I never bought into that full wedge crap, and you see that today's pros don't either, they'll hit a full 3W 40 yards short of a green now rather than laying back to 120 like they used to from 1980-2000)
The problems that await a longer layup are often enough that I just say hell with it and lay back to the 150 marker, even if that means I'm laying up with a 9i....and the 9i lay up has to be about the least interesting shot in golf. So much for giving me a more interesting second shot to that par 5. A higher handicapper is really screwed by this sort of thing. He might as well let fly with a 3W and hope he gets lucky and misses all the problems that await him, because if he lays up where I am he's got no guarantee he won't be playing his FOURTH from that minefield after chunking, topping, shanking, etc. his third. People will say that higher handicapper lacks in course management skills for not laying back of the trouble, but he's just playing the odds. Correctly, in many cases, IMHO.
I'd much rather see soft hazards like fairway contours or peninsulas of rough that extend out into the fairway, or rough islands/grass bunkers used to defend the layup area, rather than things that will cause penalty strokes. Even though the 50-80 yard bunker shot is hell for high handicappers, I think its OK because that's one shot that isn't very easy for low handicappers either. But leave an area where its possible to roll the ball by the sand, when there are 5 or 6 medium sized bunkers sprayed across the fairway such that a rolling ball will certainly find one of them, it just punishing those golfers who least need punishment.