No course is perfect. There is no such thing.
Chasing perfection later on, then, is kind of a fool’s errand. It is way more expensive and disruptive than one’s first attempt, and it is only a matter of opinion that it’s better.
If you couldn’t do something you wanted to originally and that became an option later, sure, go for it. If you built a course in your backyard in 1903, and built 300 more honing your skills afterward, sure, change whatever you want.
But those are uncommon situations. The common situation is that the course is good enough, and if it is, I believe it’s better to leave well enough alone.
I guess it depends on whether you think there is any art in golf architecture. Artists don’t want to go back and paint over their original work, or chisel a little bit off the nose. Those decisions were a moment in time, and artists respect the moment of inspiration. If they have a new idea, they just go out and create another piece of art.