I grew up in classic course-lackingTexas. I did work in Westchester for a few years and got to play many great classics. The Foot Westchester, Shinny, Quaker,Bethpage, Fishers, Maidstone, Baltimore CC, and the west coast Olympic, LA North, etc. Obviously the bulk of these couldn't handle the "modern power game" (can I add an extra point?) "of the touring professional" All of these courses gave me quite a run.
I think the ones that have held up to the "touring pro's" have no homes on the course. That allowed plenty of tree growth and to some degree takes some of the more aggressive lines away from the bombers. I also think a lot of the older courses green complexes have such a tilt to them. Built back in the day, they had sooo much tilt for a higher cut to make them quite slick. Now you cut them down to...what is it?..a 1/6th of a inch or so, you end up with quite a challenge.
Look at Winged Foot, if you miss a bit right or left and those deep bunkers kill you. If you are a bit long to protect from that miss, you are praying for a 2 putt. If you are 8 feet to the right or left pin high, do you take some of the break out and risk blowing it by 12 feet, or do you throw it up the hill and let gravity take it to the hole?
As a side note, I played a very small course in Mamaroneck the starts with a par 5. It is a down hill tee shot, then the land works back up a pretty large slope. Good players can hit a wood or, if the really crank it, a long iron. They had George Bayer would hit his drive into the slope an play a pitch into the green. The long game is not new...just more guys doing it.