That's insane that Oakmont was pushing 10" in 1977. That must have felt like 200 or something. Upper 9's (in 2021) is the best speed for the game IMO, all things considered. Downhill putts can get away from you a little bit, but uphill putts don't require a hip high to hip high stroke. I feel like I am personally at my putting best in the upper 9 range.
In regards to Oakmont, there were a couple things I found interesting as I just watched the final round today. Late I know. There were a number of holes where the players missed the fairway, and were so wide that they missed the bunkers too, and ended up with a reasonably flat lie in mowed rough. I thought this was a little odd. Two of the very best amateurs in the world missed not just the fairway, but the entire architectural corridor, and ended up in maintained turf. Shouldn't they have been in trees or shrubs or knee high grass or something? I do understand that if left and right of the fairway were all gunch, it would be absolute hell from a lost ball perspective, but it just seemed weird to me.
On the topic of playing to the wrong fairway, the look into 10 from 11 fairway (I think) was most attractive, so it's hard to fault the players for clearly intending to play over there.
To me, besides the length, and the trillion bunkers the thing that made Oakmont look so difficult was the tendency of balls to wander away from hole locations after well struck shots into greens. There were a number of times where the players hit balls to 15 feet, only to have the ball wiggle away from the pin and end up 40 feet away. I guess this is a function of greens speed, undulation, and hole location, but to me that's where Oakmont's "teeth" reside.