Of course "par" should change on a course over time.
Consider the very definition; "the score that an expert golfer should expect to make on a hole".
If we are in general agreement that expert golfers ARE becoming better, whether through technology, conditioning of courses and bodies, or whatever reason, the fact is that a hole that plays to a stroke average of less than 4.5 for expert players should probably be changed to a par four, and likewise down the par chain.
That is why "bogey" score was, and still remains, something more consistent. If an expert golfer can average, say 70 at NGLA, then there is nothing sacreligious about turning a few par fives into fours, or even a four into a three if that is reflective of reality.
All par was ever meant to be was a concept by which one could measure themselves against an expert player. It's totally absurd what it's become.
For arguments sake, let's assume that a course like Merion hosted the US Open, but instead of par 70, #2 was turned into a par four to make the course par 69. Now, 276 becomes the four day par...the expected average score of an expert player. Then, let's say that the winner shoots 270 or so, which is probably close to realistic. Instead of a winner at -10, the winner is now at -6.
Would the folks at the USGA somehow feel that par was protected better? They probably would, which is also absurd.