Before anyone gets mad at me, understand that I love and respect ALL bike builds and this is not me saying I hate modernized old bikes. When I do not like what someone has done with a bike, you will never see me actually say it or mention it because I know everyone has their own taste. This is merely my personal preference....
I look at bikes how I look at old cars. When I meet someone who says they like antique cars but they changed the motor to something electronic, added modern suspension, added modern seating with bluetooth and surround sound and did a modern metallic paint job. I would suggest they don't really love antique cars, they like an antique look but cant handle living the antique life. You wanted a modern car with an old body....
I see it the same way when someone buys a gorgeous old bike, removes the fenders, adds gears, modern seats etc etc. They want the look of an old bike but none of the hard work of riding one as it was always intended.
Me personally, and I do mean personally....I prefer not only the old bike, but the old bike experience as it was when the bike was new. I want to ride the past, not just look at it. I struggle up hills, love the rattle of the original parts, the feel of the old grips, the squeak of the old saddle and feel of the old upholstery. I even go so far as to ride on original tires when ever I can reasonably and safely do so. I will never let age or soreness get in the way of my bike looking and feeling how I want it to be. I have learned and built up a tolerance to the old ways and prefer it that way.
It all comes down to this: What do YOU want out of the experience? Do you want an old bike with modern comfort rideability? Do you want an old bike that looks like it did back in 19XX and rides the same? Either one is perfectly ok as long as when you park it at the end of the ride you think "man that was great!"
It can be very difficult to navigate the delicate scene that is the old bike scene and still care what others think, so whatever decision you make, make it with your whole heart with your experience in mind and let the wind hit your knuckles on the ride out.