I'll let you know in about 3 years

What I see is that there was a pretty huge leap from the 1950's balloon tire bikes to the 1970's 10-speeds. Perhaps also the 1950's and 1960's Raleigh 3-speeds.

There is a resurgence of an interest in the cruisers, but I think the old 1940's and 1950's cruisers are still somewhat ignored. The 3-speeds do make great city bikes, and are often dirt cheap.

Then you get to the basic 10-speeds. The QUALITY 10-speeds were somewhat rare anyway. But, for the last 50 years from the late 50's to today, there hasn't been a fundamental shift in cycling. Rather a slow accumulation of minor changes. That means my 47 yr old 10-speed is still very relevant. But, I've also chosen to slowly upgrade it over the years for a number of reasons. I've ridden the old "original" bikes, and they do feel a bit clunkier.

The much more common High-Ten 10-speeds? Vintage, I suppose, but not a lot of magic there.

However, over time, one starts to get a huge accumulation of changes.

• 1 1/8 bars/stem
• better brakes.
• Aero brakes
• Indexed shifting.
• More gears
• More relaxed gearing (in part due to more gears).
• Clinchers vs sewups.
• More rigid rims (less truing, in theory)
• Lighter & new lighter materials.
• More ergonomic handlebars.
• Stronger/more rigid frame designs.
• Cassettes
• internal cable routing
• water bottle bosses (my bike doesn't have them).

All the little changes just add up to big differences.

If I was picking out a road bike for a newbie, I'd probably do a cutoff of "brifters", or the mid 90's, and let the older bikes fall into obscurity.

They can ride the older stuff, but there really is no need.

Personally I think the friction shifters work just as well as indexed shifters, but that may not be for everyone.

One point, however, is that the majority of the changes came with accessories. So, once you get into frames with bosses, one could do well with modern parts on a 30-40 year old frame.

That may now be changing with all the high-end CF bikes. But, time will tell whether they will age gracefully, or not.