This very topic is something that we address more and more these days. Courses are land-locked and that tired old 475 yard par 5 is simply too easy for a larger portion of the membership. The Sr.'s love it, the ladies love it, but the blue tee players hate it. It is too easy. What to do? Tony's comment is very relevant. Make it a slash hole. Move the white tee back to 475 and move the blue tee forward (if desired). There are so many instances where this is happening. The reverse is true, only because some clubs think they must be par 71 or 72. So they want to take a four and make it a five. One must ask the question, "are we making a good par 4 into a crummy par 5?" All this for the sake of perception or added length.
The other issue that plays into the dynamics is golfing groups. Today you have so many different groups; scratch players, 5-10 handicappers, Sr. Men, Almost Sr. men that are still playing the wrong tee because their ego will not allow them to move up, 9-hole ladies, 18-hole ladies, Jr's (not that they have a say)............. Slashing a hole is a good solution.
We have seen holes that are long par 4's that clubs want to change because they want the extra 15 yards and 1 stroke of par. It may be better to remove an added bunker at the green, reintroduce the run-up approach (a novel idea on a long four par) and there you go. A fair, stout par 4.
Clubs also get so hung up on par, as mentioned earlier. Some should realize that by reducing par can actually gain some length for the course. Take a par 5 at 490 yards. Everyone agrees that the holes is terrible but is not sure what to do. Why not change it to a 4, shorten the hole by 20+ yards. In reality the club has gained 150-170 yards and loss a stroke of par. A par 71 course at 6600 yards may be better than the same course at par 72 and 6620 yards. Most times it is perception.
As far the USGA changing par, it is contrived many times. In the example first stated regarding Flynn, he was the original designer and was disgusted to see Pro's hitting irons into greens that were intended to be played in three shots or with longer approaches. He went to the USGA and asked that they change par. Something about technology changes in the euipment.