If one were to take a survey of ages here, I'd wager over 70% are old coots (like me). As we die off, there are less and less of us interested in vintage bikes; I suspect it's always been this way. Some young'uns will continue to come along as KOFs, but the numbers will likely continue to dwindle until, one day, all our bikes will end up in either museums or landfills.
Also, there's prolly some burnout, too - something I've experienced myself. Over the past few years I've found it difficult to get interested in bike projects of others (even here!), and I haven't purchased/built a bike since 2019. Had a good run, but today it's all about the ride for me. No more drillium, polishing, bike-buying, bike-building - just preventive maintenance and the odd consumable here and there.
If anything, resto-mods are prolly going to be the way of the future of C&V, in part because one ends up with something which represents the best of both worlds. Modern shifting and braking performance allied to a solid, reliable (and hopefully lightweight) steel or aluminum frame.
Sorry for the ramble. Just some thoughts.
DD