Interesting points of view.
For me, each bike is different. A couple of mine will always stay original, to keep their value and that great old-school feel, while my others will see mods.
For instance, my latest build, a 91 Pogliaghi, has a mix of old and new. Old is the bars, cotton bar wrap, quill stem, seat post, saddle and clip pedals, and new is wheels, a modern Campy drivetrain and brakes, but with a Velo Orange crankset. I think it came out killer looking while giving modern performance and reliability. But my 78 Colnago Super will never see upgrades like this and will remain original.
I think its fun to have both original bikes and bikes you can add your own personality.