The biggest difference is that a CF frame from that era is likely made of lugged carbon tubes- whereas all newer bikes are monocoque, and thus are fine-tuned, by having things like wall thickness and lay-up orientation, etc. customized on every inch of the frame, so that the bike can be stiff where it needs to be; compliant where it needs to be; haevy where it will be stressed; light where it doesn't matter, etc. The old CF bike were essentially built just like any other bike of it's day- only the tubes being held together by the lugs, were made out of CF instead of steel. But if it was a really good racing bike, it's still likely as good or better than half of the bikes out there today- only difference is, today, you could probably get as-good or better of a bike for a lot less money, adjusting for inflation.

No bike is magic. The differences between a mediocre bike and a great bike, are usually quite subtle. If it rides nicely and handles good, you probably wouldn't notice a huge difference going to a good modern bike, even with the drastic changes in technology which have transpired over time.